refactor neovim colors

using base16 color plugin instead of homemade

modules/common/neovim/config/colors.nix

@@ -0,0 +1,13 @@
+{ pkgs, lib, config, ... }: {
+
+  options.colors = lib.mkOption {
+    type = lib.types.attrsOf lib.types.str;
+    description = "Attrset of base16 colorscheme key value pairs.";
+  };
+
+  config = {
+    plugins = [ pkgs.vimPlugins.nvim-base16 ];
+    setup.base16-colorscheme = config.colors;
+  };
+
+}