[Doc] Misc fixes in some doc pages

[javiereguiluz]

Q	A
Branch?	2.x
Bug fix?	no
New feature?	no
BC breaks?	no
Deprecations?	no
Fixed tickets	-
License	MIT
Doc	-

Fixes these errors shown when building the docs:

Found invalid reference "../events.rst" in file "cache-resolver/aws_s3"
Found invalid reference "Imagine\Image\ImageInterface" in file "filters/general"
Found invalid reference "sys_get_temp_dir()" in file "filters/general"

[coveralls]

coverage: 82.018%. remained the same when pulling 3b9cb5f882071710e39a7309f93688fd5b90c5cd on javiereguiluz:fix_docs into 118d41993c2d47d8caf21c450c980cf00b0f88bb on liip:2.x.

[javiereguiluz]

@dbu we used Sphinx in the past, but it's hard to maintain ... so we moved from Sphinx (Python) to a custom-made and 100% PHP alternative: https://github.com/symfony-tools/docs-builder

You can see it in action here: https://github.com/symfony/symfony-docs/tree/7.1/_build

This custom-made solution used packages from other communities, like Doctrine's RST parser. Other projects like TYPO3 (https://github.com/TYPO3-Documentation) also wanted a PHP-based RST parser ... so, Doctrine, TYPO3, Symfony, etc. joined forces and there's a new tool to replace the existing one.

We don't use it yet to build Symfony docs, but I hope to use it "soon".

[dbu]

ah, glad to hear. but we won't need to change the doc format, right?

[javiereguiluz]

Correct! We still use the exact same RST syntax as before ... but now, we handle it with PHP code.