feat(fastapi): add comment actions to /account/{username}/comments

With this change, we've decoupled some partials shared between
`/pkgbase/{name}` and `/account/{username}/comments`. The comment
actions template now resolves its package base via the `comment`
instance instead of requiring `pkgbase`.

We've also modified the existing package comment routes to
support execution from any location using the `next` parameter.
This allows us to reuse code from package comments for
account comments actions.

Moved the majority of comment editing javascript to its own
.js file.

Signed-off-by: Kevin Morris <kevr@0cost.org>

templates/partials/packages/comment_form.html

@@ -13,6 +13,7 @@ Routes:
 
 <form action="{{ action }}" method="post">
     <fieldset>
+        <input type="hidden" name="next" value="{{ next }}" />
         <p>
             {{ "Git commit identifiers referencing commits in the AUR package "
             "repository and URLs are converted to links automatically." | tr }}