[docs] remove old header components, fix minor appearance regression (#20469)

[docs] Add helper components to structure installation and configuration sections (#14765)

* [docs] Add configuration helper components

* [docs] Implement new configuration components on unversio

[docs] Add helper components to structure installation and configuration sections (#14765)

* [docs] Add configuration helper components

* [docs] Implement new configuration components on unversioned notifications

* [docs] Be loud when configuration collapsibles have string content

* [docs] Add web as platform option to config plugins table

* [docs] Fix typo in unversioned notification page and implement on v43

* [docs] Add string-children check on config plugin example

* [docs] Fix missing colon in notifcations configuration example

* [docs] Use file-relative path instead of url-relative path

* [docs] Move frontmatter back to master for unversioned

* [docs] Fix linting issue

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