Can i register menus in the Explorer Navigator?

MenuContribution seems to be an Interface, could you please make it more specific?

For instance: https://github.com/kaiyue0329/theia/blob/8b3f9351473b3b6e36513dbd150cab16e6f96a1f/packages/git/src/browser/diff/git-diff-contribution.ts#L80-L84

I see, thank you very much.