`Suggestion` is missing in :Octo and :Octo actions list

[Chris Kang]

Issue Description

Type: bug report

Describe what happened (or what feature you want)

Only way to make a suggestion comment is through a key mapping.

review_diff = {
  add_review_suggestion = { lhs= "S", desc = "..."}
}

When you try to add suggestion using cmd mode, it isn't available.
Also it isnt available on "Octo actions" list

Describe what you expected to happen

:Octo comment suggest should create a new comment with suggestion

:Octo actions should show | comment | suggest | option