Add support for displaying Sixels

[marvinruder]

Closes #6748

For a quick demo, run curl https://raw.githubusercontent.com/saitoha/libsixel/master/images/snake.six

[LabhanshAgrawal]

Thanks for your contribution, I'll test it out soon.
From what I read, the addon is in beta and does not work with the latest xterm version (we're not on latest right now, but I'm working on that currently). So, it might be better to make it as a plugin instead, will have to take a deeper look to decide.

[marvinruder]

The add-on claims compatibility with xterm.js 5.1.0, which is the current stable release, but I tried it out with 5.2.0 beta and it still works there. I am open to a plug-in solution, if adding an xterm add-on is supported by one of Hyper’s extension APIs (I am not too familiar with those, but will have a look later). If not, we could also add a boolean variable to the configuration JSON for enabling/disabling the add-on.

[LabhanshAgrawal]

Oh, I saw jerch/xterm-addon-image#38 , didn't know it's fixed.

[marvinruder]

If a plug-in solution is favored, xterm.js’ loadAddon method would likely need to be exposed to plug-ins, as requested in #4560.

[jessebot]

@marvinruder and @LabhanshAgrawal thanks for your efforts on this. Really looking forward to this feature :)

[jerch]

Oh, I saw jerch/xterm-addon-image#38 , didn't know it's fixed.

Ah sorry, forgot to close the issue along with the fix.

[jerch]

Minor headsup - just added iTerm IIP support in the addon, though I consider it alpha (cannot really test&compare against iTerm2).

[LabhanshAgrawal]

Sorry, I was caught up with things, have to rethink the pr on xterm's repo for ligature fix as well, I'm thinking to merge this (with xterm v5) in the coming days, even if the ligature fix is not there yet, as anyways ligatures are disabled on electron in xterm v5 currently, so we can have few canary releases without ligatures, and then work on that instead of blocking this.
Thanks

[LabhanshAgrawal]

I've upgraded xterm to v5, please rebase.

[LabhanshAgrawal]

great work @marvinruder, also thanks @jerch for the awesome addon and your support on this pr.
Everything's looking good on local testing, just waiting for the CI.

[github-actions]

Hi there,
Thank you for contributing to Hyper!
You can get the build artifacts from here.
Here are screenshots of Hyper built from this pr.