Doc: add gdalenhance.rst (fix #8137)

[a4lamber]

What does this PR do?

add documentation for gdalenhance

What are related issues/pull requests?

#8131

Tasklist

• update gdalenhance.rst
• update the doc/requirements.txt on the sphinx-build version, there is a known bug that sphinx_rtd_theme won't be built by sphinx>7.0.0. sphinx_rtd_theme is what gdal theme based on.

Environment

Provide environment details, if relevant:

• OS:
• Compiler:

[rouault]

@a4lamber Thanks! Would you be willing contributing a autotest/utilities/test_gdalenhance.py file to test the functionality of the utility? I'm a bit nervous having public documentation of a utility that has no regression tests...

[a4lamber]

@rouault Sure, i will prob wait need some time to take a closer look at the codebase. I just start out working on gdal. If there is any additional contribution guideline, please just let me know!

[rouault]

@a4lamber any intent in doing further work on this?

[github-actions]

The GDAL project highly values your contribution and would love to see this work merged! Unfortunately this PR has not had any activity in the last 28 days and is being automatically marked as "stale". If you think this pull request should be merged, please check

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  to any issues which this pull request fixes

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