Add els build taks

Author: amiralies

.gitignore

@@ -89,4 +89,7 @@ typings/
 .dynamodb/
 
 lib/
+
+els-release/
+
 # End of https://www.gitignore.io/api/node

package.json

@@ -13,6 +13,7 @@
   "scripts": {
     "clean": "rm -rf lib/",
     "build": "webpack",
+    "els-build": "cd elixir-ls && mix deps.get && mix elixir_ls.release -o ../els-release",
     "prepack": "npm run clean && npm run build"
   },
   "repository": "github:amiralies/coc-elixir",