DOC: Add redirect for moved classes
The new redirects in this commit are for Resampler and Styler

Refactor how we do redirects. Moved all the logic into the
config file, where you state the methods / classes to be redirected.
Removed all the logic from the template, and just look up in the
new html_context variable.

Closes https://github.com/pandas-dev/pandas/issues/16186

Running a test locally ATM.
Redirects on my local build look OK.

cc @jorisvandenbossche # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16200?src=pr&el=h1) Report
> Merging [#16200](https://codecov.io/gh/pandas-dev/pandas/pull/16200?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/20fda2223d5121be3f8204702b5ce1e6037e5b18?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/16200/graphs/tree.svg?height=150&width=650&src=pr&token=eZ4WkYLtcO)](https://codecov.io/gh/pandas-dev/pandas/pull/16200?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #16200   +/-   ##
=======================================
  Coverage   90.86%   90.86%           
=======================================
  Files         162      162           
  Lines       50871    50871           
=======================================
  Hits        46225    46225           
  Misses       4646     4646
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.65% <ø> (ø)` | :arrow_up: |
| #single | `40.31% <ø> (ø)` | :arrow_up: |


------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16200?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/16200?src=pr&el=footer). Last update [20fda22...d3ca180](https://codecov.io/gh/pandas-dev/pandas/pull/16200?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
