Add a right-click context menu

[vocksel]

Right clicking on story or storybook in the sidebar opens up a context menu

1. Pin (Pin favorite Storybooks to the top #291)
2. Reload (clear cache and then reload)
3. Select in explorer
4. Preview in viewport (toggle)
5. Reset zoom

Requires #306

[vocksel]

The context menu itself should be able to be made with Foundation.Menu once #330 is merged

[vocksel]

I think for the first iteration of this I'll include Pin/Unpin and "Select in Explorer" to keep the PR small. Might squeeze in the Reload option too if it winds up being trivial to access the storybook's ModuleLoader