Added ability to subscribe/unsubscribe to community from long-press action

[hjiangsu]

Pull Request Description

This PR adds the ability to subscribe/unsubscribe to communities from the long-press action on posts. Additionally, the option to block a community from the long press action only shows up on communities that you are not currently subscribed to as it does not make sense to block a community that you have subscribed to! I also did some minor refactoring.

Note that you will have to perform a manual refresh of the feed in order for the subscription indicator to refresh on the posts.

Issue Being Fixed

Issue Number: #183

Screenshots / Recordings

Checklist

• Did you update CHANGELOG.md?
• Did you use localized strings where applicable?
• Did you add semanticLabels where applicable for accessibility?

[micahmo]

LGTM!

Will the minus icon be shown if the subscription is pending? Not sure if it's a big deal, just curious.

[hjiangsu]

Will the minus icon be shown if the subscription is pending?

Yeah it will. I'm treating the subscribed and pending statuses as nearly the same status since it doesn't really seem to affect anything at this time!