[DOCS] Adapt README file

[alexander-nitsche]

• use reST everywhere, skip markdown (GitHub also understands it)
• use template of similar extensions like EXT:extension_builder and EXT:news
• fine-tune translation with deepl.com
• add the link to the TER page of the extension to lead the user directly to the installation

Related: https://github.com/TYPO3-Documentation/T3DocTeam/issues/182

[alexander-nitsche]

Hi Armin, just became aware of your documentation rendering request today and looked by. I recommend some changes to the README file. Besides that, you might want to adapt the link in your TER page where the button "Extension Manual" links to the old documentation at https://docs.typo3.org/typo3cms/extensions/min/.

[a-r-m-i-n]

Hi Alexander, I don't want to change the root README file to rst. I'm only using rst in favoure of the documentation team infrastructure, not because I'm a fan of. I handle it in all of my extensions, like that.

But thanks for your content improvments, I will add them to current markdown version.

I also recognized, that the link is pointing to the old version, but I thought, this will update automatically, because I did not add any link to docs by myself. I'll ask the documentation team on typo3.slack.com

[a-r-m-i-n]

Oh... I just double checked it, now the link in TER works.

[a-r-m-i-n]

I'm going to close this pull request, because I've applied your content suggestions, in a separate commit.

[alexander-nitsche]

Ok, sure. I would remove the "Documentation" section in your current README.md as it seems to be a duplicate of the "Links" section.

[a-r-m-i-n]

Documentation worth to be mentioned twice! ;-)

[alexander-nitsche]

Aye, no further remarks then :)