fix: handle intermediate bytes in CSI and ESC sequences

[aymanbagabas]

This adds missing handling for CSI and ESC commands.

Fixes: #3122

[mitchellh]

Thanks, there are existing test (compilation) failures and we need to add test coverage for all of these. I'll probably push this into 1.0.1 anyways so no rush on this.

[apatterndarkly]

Real nice!

As someone who exits insert mode with ctrl+[ on several apps in the terminal, I'd been spewing ;5u all over the place for the past few hours. Fortunately that little clue led me to a work around, but yeah I'm super happy to see this fix on its way, so thank you @aymanbagabas.

For the slim chance anyone lands here with my same issue in the meantime, my workaround was to add the following to my config:

keybind = ctrl+left_bracket=text:\x1b

✌️

[aymanbagabas]

I accidentally closed the PR after force pushing the updated changes. Apparently, GitHub doesn't carry forked repository visibility settings :/

Could someone reopen the PR? Otherwise, I can create a new one

CC/ @mitchellh