DOC: Updated cookbook to show usage of Grouper instead of TimeGrouper…
Added links to show usage of Grouper and removed SO links to TimeGrouper- #16747

 - [ ] closes #xxxx
 - [ ] tests added / passed
 - [ ] passes ``git diff upstream/master --name-only -- '*.py' | flake8 --diff``
 - [ ] whatsnew entry

# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16794?src=pr&el=h1) Report
> Merging [#16794](https://codecov.io/gh/pandas-dev/pandas/pull/16794?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/664348c440ccb4dab3d4c420d6aaee7c688c9b0e?src=pr&el=desc) will **not change** coverage.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/16794/graphs/tree.svg?src=pr&token=eZ4WkYLtcO&height=150&width=650)](https://codecov.io/gh/pandas-dev/pandas/pull/16794?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #16794   +/-   ##
=======================================
  Coverage   90.93%   90.93%           
=======================================
  Files         161      161           
  Lines       49260    49260           
=======================================
  Hits        44797    44797           
  Misses       4463     4463
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.71% <ø> (ø)` | :arrow_up: |
| #single | `40.18% <ø> (ø)` | :arrow_up: |


------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16794?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16794?src=pr&el=footer). Last update [664348c...69b2398](https://codecov.io/gh/pandas-dev/pandas/pull/16794?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16794?src=pr&el=h1) Report
> Merging [#16794](https://codecov.io/gh/pandas-dev/pandas/pull/16794?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/664348c440ccb4dab3d4c420d6aaee7c688c9b0e?src=pr&el=desc) will **increase** coverage by `0.03%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/16794/graphs/tree.svg?token=eZ4WkYLtcO&height=150&src=pr&width=650)](https://codecov.io/gh/pandas-dev/pandas/pull/16794?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #16794      +/-   ##
==========================================
+ Coverage   90.93%   90.97%   +0.03%     
==========================================
  Files         161      161              
  Lines       49260    49283      +23     
==========================================
+ Hits        44797    44833      +36     
+ Misses       4463     4450      -13
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.74% <ø> (+0.03%)` | :arrow_up: |
| #single | `40.16% <ø> (-0.02%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/16794?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/common.py](https://codecov.io/gh/pandas-dev/pandas/pull/16794?src=pr&el=tree#diff-cGFuZGFzL2lvL2NvbW1vbi5weQ==) | `67.79% <0%> (-2.12%)` | :arrow_down: |
| [pandas/core/indexes/datetimes.py](https://codecov.io/gh/pandas-dev/pandas/pull/16794?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9kYXRldGltZXMucHk=) | `95.23% <0%> (-0.1%)` | :arrow_down: |
| [pandas/core/indexes/base.py](https://codecov.io/gh/pandas-dev/pandas/pull/16794?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9iYXNlLnB5) | `95.8% <0%> (-0.01%)` | :arrow_down: |
| [pandas/core/window.py](https://codecov.io/gh/pandas-dev/pandas/pull/16794?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvd2luZG93LnB5) | `96.49% <0%> (ø)` | :arrow_up: |
| [pandas/core/groupby.py](https://codecov.io/gh/pandas-dev/pandas/pull/16794?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ3JvdXBieS5weQ==) | `92.07% <0%> (ø)` | :arrow_up: |
| [pandas/core/indexes/multi.py](https://codecov.io/gh/pandas-dev/pandas/pull/16794?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9tdWx0aS5weQ==) | `96.65% <0%> (ø)` | :arrow_up: |
| [pandas/io/formats/format.py](https://codecov.io/gh/pandas-dev/pandas/pull/16794?src=pr&el=tree#diff-cGFuZGFzL2lvL2Zvcm1hdHMvZm9ybWF0LnB5) | `96.03% <0%> (ø)` | :arrow_up: |
| [pandas/core/reshape/merge.py](https://codecov.io/gh/pandas-dev/pandas/pull/16794?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvcmVzaGFwZS9tZXJnZS5weQ==) | `94.2% <0%> (+0.01%)` | :arrow_up: |
| [pandas/core/generic.py](https://codecov.io/gh/pandas-dev/pandas/pull/16794?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ2VuZXJpYy5weQ==) | `92.29% <0%> (+0.02%)` | :arrow_up: |
| [pandas/core/dtypes/common.py](https://codecov.io/gh/pandas-dev/pandas/pull/16794?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZHR5cGVzL2NvbW1vbi5weQ==) | `94.79% <0%> (+0.04%)` | :arrow_up: |
| ... and [6 more](https://codecov.io/gh/pandas-dev/pandas/pull/16794?src=pr&el=tree-more) | |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16794?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16794?src=pr&el=footer). Last update [664348c...9448f98](https://codecov.io/gh/pandas-dev/pandas/pull/16794?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 thanks!