.aliases: Add `chromekill` to kill all Chrome tabs to free up memory

Useful when you have a lot of tabs open (which I always do), but you don’t want to close them.

Tabs in Chrome are just processes, so we just filter out the ones we want, and kill them.

Closes #236.
Merge commit 'bd9429af1cfdc7f4caa73e6f98773ed69a161c9c'

# By Sindre Sorhus
# Via Mathias Bynens
* commit 'bd9429af1cfdc7f4caa73e6f98773ed69a161c9c':
  .aliases: Add `chromekill` to kill all Chrome tabs to free up memory

Conflicts:
	.aliases