Add a context menu

[jecaro]

This PR adds a very simple context menu to Termonad #12.

For now I've put only copy/paste items. But adding existing actions to the menu is pretty straight forward.

I've worked a bit on adding an action to open an url in a navigator. It's not as easy at it seems for two reasons:

• Some annotations in Vte functions are missing but I sent a PR to fix it Add missing annotations for Vte functions haskell-gi/haskell-gi#265
• It requieres to cast EventButton to Event to be able to call terminalMatchCheckEvent and it's not currently supported by haskell-gi. This issue How can we convert EventMotion to Event? haskell-gi/haskell-gi#109 is exactly the same as the one I run on. There is a workaround decribed in the issue thought.

[cdepillabout]

@jecaro Sorry for not getting to this right away. I've been traveling and I may not have a time to really take a look at this for another week or so.

However, after taking a quick look at it, I think this is looking pretty good.

Also, thanks a lot for fixing stuff upstream. You may want to reply to haskell-gi/haskell-gi#109 just making sure that garetxe knows there is someone else blocked on this.

(Or you might be interested in actually fixing haskell-gi/haskell-gi#109 upstream as well? I'm sure garetxe would appreciate the help.)

[cdepillabout]

Also, @mimi1vx, it looks like you added a 👍, so if you wanted to review this, I'd appreciate the additional eyes on this!

[jecaro]

You're right @cdepillabout , I just sent a comment on the issue.

Take your time reviewing this, there is no hurry, and enjoy your trip !

[cdepillabout]

This has been implemented in #136.