Add command for displaying image streams

[NicoBiernat]

Some things that could be improved / changed:

• use futures instead of polling the stream and key events
• integrate this into the "cat" command
• add a border and title around the display

[fwcd]

Thanks, this looks pretty cool and I look forward to having a way of viewing streamed frames graphically in real-time! I have left some, mostly technical notes, below.

One remark:

integrate this into the "cat" command

That's an interesting idea, but I would probably keep it in a separate command, just to keep things simple and because there doesn't seem to be an obvious Unix analogon to this functionality.

[NicoBiernat]

The application still hangs after a while for unknown reasons...

[fwcd]

Thanks again!

I have merged the changes from the main branch, which updates lighthouse-client to 3.4.0. In my tests, it seems to run pretty reliably, so hopefully these issues are fixed. If not, feel free to open another issue.

The canvas now uses a custom Shape implementation that makes sure to render the display at an integer scale to make sure that no rows or columns are skipped. Finally, the display now also forwards all key strokes other than q (which quits the command) as input events to the server, enabling games etc.