Add support for Vimeo videos

[ChrisMBarr]

Now videos from Vimeo.com can be added to a gallery just like YouTube by simply provide the video ID from the URL. For example this video: https://vimeo.com/124139626 is embedded like so:

{
  type: 'vimeo',
  autoplay: false,
  src: '124139626'
} as VimeoItemData,

Here's a screen recording of that Vimeo video working on the demo page.

Searching through old issues, this addresses additional concerns already addressed by #22, and might possibly address #539

The only thing not covered by this PR is updating all the wiki pages that mention youtube to also have mentions and code examples of Vimeo as well.

[ChrisMBarr]

I have resolved the merge issues since the v11 update, and I've tested this, and it's still working just fine.

Some logic around fetching a Vimeo thumbnail got a lot simpler than before, I opened an issue over there and it was resolved. For reference: ThatGuySam/vumbnail#42