[DOCS] Adds compatibility matrix to docs and readme

[szabosteve]

Overview

This PR adds a compatibility matrix to the Overview section of the Python book and the repo readme. It also fixes the markup of the links at the top of the Installation page.

Preview

• Compatibility
• Installation

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[pquentin]

Thanks! Should we also update https://github.com/elastic/elasticsearch-py/blob/main/docs/sphinx/index.rst#compatibility?

[szabosteve]

Should we also update https://github.com/elastic/elasticsearch-py/blob/main/docs/sphinx/index.rst#compatibility?

Yes, definitely! Thank you for the heads-up! I updated via 625c6fb.

[pquentin]

The tables do not render correctly in reST:

• Read the Docs: https://elasticsearch-py--2458.org.readthedocs.build/en/2458/#compatibility
• GitHub: https://github.com/elastic/elasticsearch-py/blob/625c6fb3c0f676241d27f4f84b766fa2d152b127/README.rst

According to https://www.sphinx-doc.org/en/master/usage/restructuredtext/basics.html#tables, you're missing the separation between the lines (+---+---+---+).

[pquentin]

Also, can you please change the casing as below? elasticsearch-py isn't capitalized. Thanks and sorry for all the nitpicks.

[szabosteve]

Thanks for all the work on this, @pquentin! BTW, tables are killing me.

[pquentin]

Thanks for iterating! LGTM.