[Feature] Add title attribute to buttons in the Note Menu Bar to help understand of the buttons purpose

[bjankord]

Problem Upon first use, it can be tricky to understand what the buttons in the Note Menu Bar do.

Solution By adding a title attribute to the button with a name for the button, users could hover over the button and see what the intent of the button is, whether its for Markdown Preview, Download, etc.

[bjankord]

@taniarascia If you are cool with this feature, I can send a PR.

[taniarascia]

Sure, that sounds good, a tooltip for the buttons.