Add the context menus to macOS and Windows.

[quadrupleslap]

Right now, macOS has context menus, but it won't after implementing the only known fix to #1. Unfortunately, Windows doesn't have context menus, either. Context menus are obviously important.

[fullreset]

But since such menus can be emulated in the webview itself is this really that important?

[I originally said 'implemented' but meant emulated.]

Of course if the point is to access OS features (rather than application features) then I do agree -- it is of value.

[quadrupleslap]

Yes, the point is to access standard context menu items - on Linux, you can still play, pause, copy, paste, etc. using the context menu - it's only navigation items that've been removed. On Windows and macOS, Tether just disables the context menu, because those platforms don't have an API for whitelisting context menu items.