Feature Request: Add settings for modifying annotation indicators

[SidIcarus]

Rationale: Allow those who follow JSDoc or similar documentation conventions, @ to have highlighting.

Current:

• Alert: !
• Queries: ?
• Todo: TODO
• Removed: ////
• Description: (none?)

Proposed: (defaults written in)

better-comments.annotations: {
  alert: ['!'],
  queries: ['?'],
  todo: ['TODO'],
  removed: ['////'],
  description: [' '],
}

I suggest an array so that if people want to have multiple annotations be highlighted identically, such as both ['TODO', '@todo', '@todo'], it'll be feasible.

[aaron-bond]

This FR kicked off an absolute brain fart of a changeset, but it got there eventually. See: 0e7eab9

Push to marketplace coming ASAP