chore: use workspaces, fix deps

react-monaco-editor needed rolling back due to an incompatibility with
react 16
monaco-editor then needed rolling back and the editor config, too.

Some @types needed to be added, some lint deps needed updating.

client/webpack-workers.js

@@ -62,7 +62,7 @@ module.exports = (env = {}) => {
     },
     plugins: [
       new CopyWebpackPlugin({
-        patterns: ['node_modules/sass.js/dist/sass.sync.js']
+        patterns: ['../node_modules/sass.js/dist/sass.sync.js']
       }),
       new webpack.ProvidePlugin({
         process: 'process/browser'