- Linting: Comment out unused var.

- Maintenance: Add `.editorconfig`
- npm: Update jml, core-js-bundle, devDeps

.editorconfig

@@ -0,0 +1,16 @@
+; EditorConfig file: https://EditorConfig.org
+; Install the "EditorConfig" plugin into your editor to use
+
+root = true
+
+[*]
+charset = utf-8
+end_of_line = lf
+insert_final_newline = true
+indent_style = space
+indent_size = 2
+trim_trailing_whitespace = true
+
+; [app/public/css/**.styl]
+; indent_style = tab
+; indent_size = 2