Mark articles with category tags

The MediaWiki provides a way to tag articles (at the end of the article). We are using this feature to structure the Wiki.

Elements of the Nix Ecosystem should be tagged by one or more of the following categories:

[[Category:NixOS]]: Articles related to the Nix operating system, the module system and the system configuration.
[[Category:Nix]]: Articles about using the Nix Tools to accomplish great things.
[[Category:Nixpkgs]]: Articles about maintaining code in the Nixpkgs repository, structuring, and so on.
[[Category:Nix Language]]: Description of language quirks and solutions.
[[Category:Hydra]]: Articles about Hydra continuous Integration related documentation.
[[Category:Application]]: Extended Ecosystem: Articles about other Nix-based or Nix-related applications.

Almost all content of the wiki can be accessed with 2 to 3 clicks via one of these topic categories:

[[Category:Software]]: Articles about software applications like neovim or libreoffice
[[Category:Hardware]]: Articles about hardware like GPU, keyboards and notebooks.
[[Category:Desktop]]: Articles about using NixOS on a PC (e.g. desktop environments)
[[Category:Server]]: Articles about using NixOS on servers, like running web applications (e.g. Nextcloud)
[[Category:Community]]: Articles about the Nix(OS) community and how to engage and contribute.

The type of documentation for new pages should be tagged with one of the following categories: