Neovim, refactor to use modules, lua, and LSP

Refactors the neovim config to use nix modules, and changes the plugins
to favor the builtin neovim LSP over COC. Changes all code to use lua
code instead of vimscript.

hmModules/apps/neovim/plugin/treesitter.nix

@@ -0,0 +1,30 @@
+{ config, pkgs, lib, ... }:
+
+let
+  cfgp = config.neovim.plugins;
+  cfgl = config.neovim.languages;
+in {
+  config = lib.mkIf (config.neovim.enable && cfgp.treesitter.enable)  {
+    programs.neovim.plugins = let
+      configText = ''
+        require('nvim-treesitter.configs').setup {
+          ensure_installed = {},
+
+          auto_install = false,
+
+          highlight = { enable = true },
+
+          indent = { enable = true },
+        }
+      '';
+
+      treeplugs = p: lib.lists.optional cfgl.nix.enable p.tree-sitter-nix;
+    in with pkgs.vimPlugins; [
+      {
+        plugin = (nvim-treesitter.withPlugins treeplugs);
+        type = "lua";
+        config = configText;
+      }
+    ];
+  };
+}