nemo-preview: init at 6.4.0, xreader: enable introspection

[BeatLink]

This PR adds the nemo-preview extension to the Nemo file manager. By selecting a file and pressing spacebar, nemo-preview allows the contents of the file to be displayed.

See https://github.com/linuxmint/nemo-extensions/tree/master/nemo-preview

In order for nemo-preview to work, this also requires GTK introspection to be enabled for xreader. This PR also implements that change

Closes #373218

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • sandbox = relaxed
  • sandbox = true
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 25.05 Release Notes (or backporting 24.11 and 25.05 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

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Add a 👍 reaction to pull requests you find important.

[mkg20001]

Also please rebase properly. git rebase -i NixOS/master (or whatevef the remote is called)

I just saw you have a merge commit in your history

[awwpotato]

There should only be one commit, nemo-preview: init at 6.4.0. This includes not having the merge commit, instead you should rebase.

[BeatLink]

What is the command to rebase?

[bobby285271]

Thanks. I am fine to maintain this.