Add support for ISSO comments

[rnbwdsh]

Checklist

• I have read and accepted the contributing guidelines.

Is your feature request related to a problem? Please describe

Currently, all the comment options are somewhat linked to github, not really for "true self hosted" with little effort, not free or bloated.

Describe the solution you'd like

I'd like comment functionality support for ISSO

Describe alternatives you've considered

The existing 3 solutions + cusdis (also fine, but 2.6k stars vs 5k stars on gh)

Additional context

I already made a PR to show it off.
#2711