completely refactor and modularize flake

modules/default/common/nixvim/illuminate.nix

@@ -0,0 +1,18 @@
+{ ... }:
+{
+
+  programs.nixvim.plugins = {
+    illuminate = {
+      enable = true;
+      underCursor = false;
+      filetypesDenylist = [
+        "Outline"
+        "TelescopePrompt"
+        "alpha"
+        "harpoon"
+        "reason"
+      ];
+    };
+  };
+
+}