TouchBar support

[romainlq]

As mentioned on the Slack general channel, it would be great to add support for 2016-17 MacBook Touch Bar.

This issue could be used to add suggestions on what could be interesting to add on this Touch Bar

[robbawebba]

I would love to see some basic markdown editor controls while in edit mode:

• create an ordered/unordered list
• start a todo list
• bold, underline, italics
• insert a markdown link
• insert a code block

All of these couldn't fit in the touch bar, so some of them might have to be left out or condensed.

[mikaoelitiana]

This is a great feature to have. A quick link to note category would be great also.