[Sempahore] Added first round of documentation

[lyrixx]

refs #14139

[lyrixx]

@noniagriconomie Thanks for your feedback. I have addressed them

[noniagriconomie]

Top, just i do not understood the « new Redis() » part, can you explain? Thx

[andrew-demb]

@noniagriconomie this class available with redis extension - https://github.com/phpredis/phpredis#classes-and-methods

[noniagriconomie]

I see better thx

[noniagriconomie]

i just do not know if for the documentation it should be mentioned that the component is experimental for now in this version :)

[wouterj]

Hi @lyrixx! Thanks for providing a documentation PR.

In the docs, we're slowly migrating to focus on framework usage. This means that instead of writing component documentation, we write framework guides. Do you maybe have time to update this documentation to instead be in /semaphore.rst and focus on how to use the Semaphore component in the framework? (this probably means telling how to register specific services, as I can't find framework integration yet)

i just do not know if for the documentation it should be mentioned that the component is experimental for now in this version :)

Yes, that should be mentioned :) See the 5.0 version of the string documentation for an example:

symfony-docs/components/string.rst

Lines 11 to 14 in a7e9a6f

	.. versionadded:: 5.0
	The String component was introduced in Symfony 5.0 as an
	:doc:`experimental feature </contributing/code/experimental>`.

[javiereguiluz]

Grégoire, thanks for contributing this feature and its docs too. This is now merged!