DOC: Accessing files from a S3 bucket.
Add some documentation about accessing files from a remote S3 bucket in pandas.

- [x] closes #12206
- [x] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/23639?src=pr&el=h1) Report
> Merging [#23639](https://codecov.io/gh/pandas-dev/pandas/pull/23639?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/b9ba7085983bd287ef08963bffbb5acf964db041?src=pr&el=desc) will **decrease** coverage by `<.01%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/23639/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/23639?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #23639      +/-   ##
==========================================
- Coverage   92.24%   92.24%   -0.01%     
==========================================
  Files         161      161              
  Lines       51326    51314      -12     
==========================================
- Hits        47347    47335      -12     
  Misses       3979     3979
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.63% <ø> (-0.01%)` | :arrow_down: |
| #single | `42.31% <ø> (-0.02%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/23639?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/common.py](https://codecov.io/gh/pandas-dev/pandas/pull/23639/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2NvbW1vbi5weQ==) | `70.54% <0%> (-0.23%)` | :arrow_down: |
| [pandas/io/parquet.py](https://codecov.io/gh/pandas-dev/pandas/pull/23639/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL3BhcnF1ZXQucHk=) | `84.61% <0%> (-0.15%)` | :arrow_down: |
| [pandas/io/html.py](https://codecov.io/gh/pandas-dev/pandas/pull/23639/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2h0bWwucHk=) | `91.2% <0%> (-0.06%)` | :arrow_down: |
| [pandas/core/series.py](https://codecov.io/gh/pandas-dev/pandas/pull/23639/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvc2VyaWVzLnB5) | `93.68% <0%> (-0.03%)` | :arrow_down: |
| [pandas/io/json/json.py](https://codecov.io/gh/pandas-dev/pandas/pull/23639/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2pzb24vanNvbi5weQ==) | `93.09% <0%> (-0.02%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/23639/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.02% <0%> (-0.01%)` | :arrow_down: |
| [pandas/io/parsers.py](https://codecov.io/gh/pandas-dev/pandas/pull/23639/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL3BhcnNlcnMucHk=) | `95.55% <0%> (-0.01%)` | :arrow_down: |
| [pandas/tseries/offsets.py](https://codecov.io/gh/pandas-dev/pandas/pull/23639/diff?src=pr&el=tree#diff-cGFuZGFzL3RzZXJpZXMvb2Zmc2V0cy5weQ==) | `97.07% <0%> (-0.01%)` | :arrow_down: |
| [pandas/core/groupby/ops.py](https://codecov.io/gh/pandas-dev/pandas/pull/23639/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ3JvdXBieS9vcHMucHk=) | `96.79% <0%> (ø)` | :arrow_up: |
| [pandas/plotting/\_core.py](https://codecov.io/gh/pandas-dev/pandas/pull/23639/diff?src=pr&el=tree#diff-cGFuZGFzL3Bsb3R0aW5nL19jb3JlLnB5) | `83.63% <0%> (ø)` | :arrow_up: |
| ... and [4 more](https://codecov.io/gh/pandas-dev/pandas/pull/23639/diff?src=pr&el=tree-more) | |

------

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 This looks good to me - CC. @jreback and @datapythonista  We already have this: https://pandas.pydata.org/pandas-docs/stable/io.html#reading-remote-files

I'd expand that section if there is anything missing, I wouldn't expect many people to look in the cookbook for S3 options having a page specific for IO operations.

Does it make sense? @datapythonista I've expanded the the section in io and remove it from cookbook. thanks!