Sync comment edits (in both directions)

[janbaykara]

For an issue created in Github, then synced to Linear, comment edits are not being synced either from Linear to Github or Linear to Github.

The same problem might be occurring for issues created in Linear but I can't test this before #43 is resolved.

[jtormey]

I think I made this decision intentionally, in case maintainers wanted to edit and add information that should be private. However I agree this would be a useful option to have!