Refactor Mastodon Comments

[luizdepra]

Describe the enhancement

Mastodon Comments should:

• Only add Mastodon CSS if needed. Maybe move mastodon styles to a separated file.
• The CSS style should match the theme style.
• Configuration should be:

[params.mastodon]
purityPath = "..."
host = "..."
username = "..."
postId = "..."

• Posts could override the configuration with any combination of host, username and postId.

[mastodon]
host = "..."
username = "..."
postId = "..."

• Add an option to load comments automatically.
• Add documentation about how to use this feature.

[retiolus]

There is an issue displaying user's avatar, I don't know why but with hugo server it looks right:

But after a hugo -D it looks like this:

[retiolus]

Also, the "Learn how this is implemented link" is broken