Prepare for 5.0.9-prerelease
Add @buggj's plugin site to the Community tiddler
Add docs for tw-close-other-tiddlers message

Fixes #461
Improve the descriptive text for missing tiddlers

Now we explain that it’s a missing tiddler, and add a “create” button
Docs update
Add docs for keyboard widget
Force the highlight language to lower case
Allow middle mouse button to trigger navigation suppression when clicking a tiddler link

Equivalent to holding control/command while clicking.
Add chinese translation of MissingTiddler stuff in Misc.multids.