Forem: Add link to /community-moderation on all /mod pages

[michael-tharrington]

It's difficult to find links to the community moderation guide (dev.to/community-moderation), so it'd be valuable to add this link to various relevant pages.

We should add this link - https://dev.to/community-moderation to any /mod page:

1. https://dev.to/mod
2. https://dev.to/dev-username/article-title/mod

Additional context

1. Suggestion on where to put link on /mod:

1. Suggestion on where to put link on /dev-username/article-title/mod:

[juliegoat]

I would love to take on this one! Working on it now :)