Support submitting comments to WordPress

[ThierryA]

Acceptance Criteria

AC1: The commenting experience that is native to WordPress needs to be supported in the AMP theme.
AC2: A user will need the ability to access the comment form, enter comment, and successfully submit a comment, as they do today.

Tasks

• Add comment list template
• Add comment form template + submission

[alcurrie]

These are the same notes as in #862
Functionality looks good and works well, but I noticed a few items that were not as expected:

1. Issue: Comment moderation does not display comments for previously approved comment authors.
   Expected
   In the Discussion Settings, when the Before a comment appears: Comment must be manually approved (is 'unchecked'), and Comment Author must have a previously approved comment is checked (See screen cast of settings https://cl.ly/442k1O2z1J0b)
   I expect that when I enter the same Name and email as a user whose comments have already been approved, that my comment will display right away.
   Actual
   Even if the comment author has been previously approved, comment does not display.

2. The confirmation of the comment post, is too close to the Post comment button:
   

3. From a usability perspective the comments seem quite far away from the actual article with several other articles between the bottom of the article the user is commenting on, with 3 other articles between the article and the comments on the article
   https://cl.ly/1x0g0H0K421k

[csossi]

see Anne Louise's comments above