move clipboard.js to npm/webpack (#10183)

- created lazy-loaded webpack chunk for clipboard.js
- upgraded clipboard.js from 1.5.9 to 2.0.4
- parallelize initialization of all lazy-loaded features

Co-authored-by: Antoine GIRARD <sapk@users.noreply.github.com>

.eslintrc

@@ -18,7 +18,6 @@ env:
 
 globals:
   __webpack_public_path__: true
-  Clipboard: false
   CodeMirror: false
   Dropzone: false
   emojify: false