plugins/git: add vim-fugitive; modularize

modules/plugins/git/default.nix

@@ -1,6 +1,18 @@
-{
+{lib, ...}: let
+  inherit (lib.options) mkEnableOption;
+in {
   imports = [
-    ./config.nix
-    ./git.nix
+    ./gitsigns
+    ./vim-fugitive
   ];
+
+  options.vim.git = {
+    enable = mkEnableOption ''
+      git integration suite.
+
+      Enabling this option will enable the following plugins:
+      * gitsigns
+      * vim-fugitive
+    '';
+  };
 }