docs(documentation): add future references for mdBook maintenance

docs/src/websites/documentation.md

@@ -18,13 +18,23 @@ mdbook serve --open # the latter additionally opens the website in a browser
 
 ## Useful information
 
+### mdBook syntax
+
 While the general syntax for writing Markdown applies to mdBook, it has several extensions beyond the standard CommonMark specification.
 
 - [Markdown syntax](https://rust-lang.github.io/mdBook/format/markdown.html)
 - [mdBook specific features](https://rust-lang.github.io/mdBook/format/mdbook.html)
 
 Especially importing code blocks as Markdown is really handy to keep content always up-to-date and helps providing a full text searchable code documentation.
 
+### Updating mdBook plugins contents
+
+Some of the mdBook parts are plugins that need their content to be updated from time to time. Namely, thats:
+
+- mdbook-admonish: run `mdbook-admonish` inside the `docs` folder
+- mdbook-emojicodes: works without CSS, so no updates needed
+- mdbook-catppuccin: run `mdbook-catppuccin` inside the `docs` folder (might need to grab binary from [its website](https://github.com/catppuccin/mdBook/releases), no Nix package available yet)
+
 ## Deployment
 
 Deployment to Cloudflare pages automated and happens whenever a commit to main occurs.
@@ -33,3 +43,14 @@ A [GitHub actions workflow](https://github.com/garuda-linux/infrastructure-nix/b
 ```yaml
 {{#include ../../../.github/workflows/pages.yml}}
 ```
+
+## Issues and their solution
+
+### Sidebar or something else on the documentation doesn't work as expected
+
+Chances are that the custom CSS parts need to be rebased to a newer version.
+They can be found in `./docs/theme/css` and the only addition we made here is to use the Fira Sans font instead of the default one.
+To rebase against a newer version comment out `dditional-css` in `./docs/book.toml` and move the `css` folder somewhere else temporarily.
+After that, run `mdbook build` inside the `docs` folder. The new CSS files can now be found inside the `./docs/book/css` folder.
+Copy those to the `./docs/theme/css` folder and alter the occurrences of font settings to include Fira Sans (or run a diff to find out where).
+After uncommenting `additional-css` in `book.toml`, run `mdbook build` again to verify nothing got broken along the way.