Allow overriding area repr map section HTML

[djhoese]

These changes help control how AreaDefinitions and others are represented when plotted for sphinx documentation (specifically Satpy). See https://github.com/pytroll/satpy/issues/2864 for more information. No TDD on this one.

CC @BENR0

• [ ] Closes #xxxx
• [ ] Tests added
• [ ] Tests passed
• [ ] Fully documented

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 96.77419% with 1 line in your changes missing coverage. Please review.

Project coverage is 93.97%. Comparing base (0a47fd3) to head (8002a7a). Report is 6 commits behind head on main.

Files	Patch %	Lines
pyresample/_formatting_html.py	92.85%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #615 +/- ## ========================================== - Coverage 93.97% 93.97% -0.01% ========================================== Files 86 86 Lines 13819 13825 +6 ========================================== + Hits 12987 12992 +5 - Misses 832 833 +1 ``` | [Flag](https://app.codecov.io/gh/pytroll/pyresample/pull/615/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pytroll) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/pytroll/pyresample/pull/615/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pytroll) | `93.97% <96.77%> (-0.01%)` | :arrow_down: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pytroll#carryforward-flags-in-the-pull-request-comment) to find out more.

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[coveralls]

coverage: 93.676% (-0.004%) from 93.68% when pulling 8002a7a3482b99afad01e74e392aedf24edf9d05 on djhoese:feat-html-bokeh into af0d4cc73bed0b8fc06bbe55d2532a12b1dda49b on pytroll:main.