feat: add pug-lsp support (#3220)

lua/lspconfig/server_configurations/pug.lua

@@ -0,0 +1,18 @@
+local util = require 'lspconfig.util'
+
+return {
+  default_config = {
+    cmd = { 'pug-lsp' },
+    filetypes = { 'pug' },
+    root_dir = util.find_package_json_ancestor,
+  },
+  docs = {
+    description = [[
+https://github.com/opa-oz/pug-lsp
+
+An implementation of the Language Protocol Server for [Pug.js](http://pugjs.org)
+
+PugLSP can be installed via `go get github.com/opa-oz/pug-lsp`, or manually downloaded from [releases page](https://github.com/opa-oz/pug-lsp/releases)
+    ]],
+  },
+}