Improved user guide, added CI vale for docs (#2308)

* restructured user guide, minor fixes

* added index file for user guide

* github actions for vale

* testing workflow

* CI vale

* changes as per vale's suggestions

* set CI vale on pull request

* adding homebrew script to macos infra setup file

* fix CI errors

* testing vale

* testing vale

* testing vale

* testing vale

* testing vale

* testing vale

* testing vale

* testing vale

* testing vale

* testing vale

* testing vale

* testing vale

* testing vale

* testing vale

* testing vale

* testing vale

* testing vale

* testing vale

* vale testing complete

* vale cleanup

* vale test

* vale test for github-pr-check

* vale test for github-pr-check

* vale test for github-pr-check

* vale test for github-pr-check

* testing vale warnings

* testing vale warnings

* testing vale warnings

* testing vale warnings

* testing vale warnings

* testing vale warnings

* testing vale warnings

* swizzled doc cards to add icons

* Align CI params to other CIs

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Co-authored-by: Félix Malfait <felix.malfait@gmail.com>

.github/styles/docs/SentenceLength.yml

@@ -0,0 +1,6 @@
+extends: occurrence
+message: "Try to keep sentences short (< 30 words)."
+scope: sentence
+level: suggestion
+max: 30
+token: \b(\w+)\b