demos: Rename demos.html to index.html for convenience

Follows-up b8124715566bd3d2. There's only one html file now,
might as well have it be the index.

Change-Id: Ibd7a8ad0330bd3c2f46538a155ce951cea5745ff
demos: Add example of menu item with a long label

Demonstrates the ellipsis being applied.

Change-Id: Ibb9fc11f797a8c18fb496fcd4b9546893f0c88f4
Update oojs to v1.0.11

Code:
 https://oojs.github.io/releases/oojs-1.0.11.js

Release notes:
 https://git.wikimedia.org/blob/oojs%2Fcore.git/v1.0.11/History.md

Change-Id: I0ff667c59e0a1e97d29481f7423c6b367510793a
Merge "demos: Rename demos.html to index.html for convenience"
Merge "demos: Add example of menu item with a long label"
Merge "Update oojs to v1.0.11"