chore: Refactor file structure and dependencies

- Add `versionToolPackage` variable to simplify code
- Update references to `versionTool` to use `versionToolPackage`
- Fix typo in the `docman` package description
- Update `vendorSha256` value to match new dependencies
- Add `ldflags` to `docman` build options
- Add `buildInputs` for `versionToolPackage` in `docman`
- Add metadata for `docman` package
- Reviewed and made changes in multiple files
- Improved code readability and maintainability

flake.nix

@@ -32,10 +32,11 @@
 #        # You'll need to provide the correct hash here.
 #        sha256 = "sha256-jzixQKFFW4oxO0S4GYqbkFCXzhBd6com6Z9+MtVKakU=";
 #      };   
+     versionToolPackage = versionTool.defaultPackage.${system};
 
      versionAndBuild = pkgs.runCommand "get-version-and-build" {} ''
-        ${versionTool}/bin/version print --git > $out.version
-        ${versionTool}/bin/version build > $out.build
+        ${versionToolPackage}/bin/version print --git > $out.version
+        ${versionToolPackage}/bin/version build > $out.build
       '';