Mouse support via DEC Locator mode

[gwpl]

I tried in ttyd on Linux running and mouse was not detected:

Drawing Example This example suggests how to implement the interaction among SIXEL terminals and pointer devices. https://github.com/saitoha/libsixel/tree/master/examples/drawing

Not sure if problem is in example or in xterm.js or ttyd, so making ticket on each repo and cross linking:

https://github.com/tsl0922/ttyd/issues/1422 https://github.com/xtermjs/xterm.js/issues/5310 https://github.com/saitoha/libsixel/issues/186 (I never know what's the right way of making issue that are across repositories 🙈 , if there is any "right way")