Add a way to set a custom comment

[urielsalis]

No description provided.

[SunCatMC]

could it be done through "secret" discord channel? so it's not open for everyone to tinker with

[SPGoding]

If we decide to keep the current design of re-generating RedditPost from 0 every time, we could add a new comments.json file to store a map from ticket IDs to custom comments, so that these comments can be kept.

Or we could change the current design and make r/isa keep our custom comments (and maybe other custom information, e.g. the beginning of the post so #26 could also be partially solved) between edits.