Appending comments

[nedtwigg]

• after making a comment with gitcasso enabled, it turns into this #76

[nedtwigg]

• for an issue thread
  • every comment creates a new textarea, and deleting the old preview is the key to good a result
  • easiest thing is to delete very preview where the textarea is dynamically killed, and that's probably a good policy regardless
• for a PR thread
  • it turns out that there's only one textarea for every appended comment
  • when you append a comment, it reuses the textarea
  • listening to input events doesn't work
  • Mutation Observer does. Huzzah!