Write documentation for the Cache component

[RCheesley]

We need to bring over the docs from the old docs relating to the Caching bundle, ensure that it's up to date, and write it in RST format.

https://developer.mautic.org/#cache-bundle

[dennisameling]

@escopecz are the old docs referenced above still valid? If yes, I can port them over to RST 👍🏼

[escopecz]

Yes, the CacheBundle is still the latest way how to cache stuff. The docs seem to be incomplete. Mostly missing an example. I found only one usage of the CacheHelper though in https://github.com/mautic/mautic/blob/5.x/app/bundles/MarketplaceBundle/Service/Allowlist.php#L31 so it really needs some attention :)

[mautibot]

This issue has been mentioned on Mautic Community Forums. There might be relevant details there:

https://forum.mautic.org/t/configuring-memcache-or-redis-in-local-php/27267/2

[mautibot]

This issue has been mentioned on Mautic Forums. There might be relevant details there:

https://forum.mautic.org/t/post-thanksgiving-boost-contribute-to-mautic-this-open-source-friday/30038/1

[fakela]

#172