Ability to filter posts containing keyword in title/body

[hjiangsu]

Pull Request Description

Review with whitespace off

This PR enables the ability to add and remove keywords. When adding keywords, any post that contains the keyword in the title or body will be filtered out from the feed page (and any widget that uses the feed page).

Some additional notes:

• Added width: min(MediaQuery.of(context).size.width, 700) to showThunderDialog's AlertDialog. This allows alert dialogs to take up more of the width of the screen similar to the input dialogs (community, user, instance, etc)
• Applied some small UI tweaks to UserSettingsPage since it now appears on the Settings page, I've adjusted some of the UI for blocking users/communities/instances to match the other UIs present in the Settings page.

Issue Being Fixed

Issue Number: #513

Screenshots / Recordings

Simulator.Screen.Recording.-.iPhone.15.Pro.-.2023-12-12.at.11.41.12.mp4

Checklist

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

[hjiangsu]

@micahmo ready for review!

[micahmo]

Awesome feature!

One thing I noticed while testing... This might be a problem I introduced with my dialog refactor, but I was able to add an empty string as a filter by pressing enter on the keyboard. (I think this is a problem with the comment search too.)

[hjiangsu]

I was able to add an empty string as a filter by pressing enter on the keyboard

Ahh, I missed that edge case while testing it. I can add in an additional check to make sure we can't add in empty strings (and also trim whitespaces while I'm at it)

[hjiangsu]

Added trimming to showInputDialog to disable the button when there's empty strings, and added trimming to keywords in eff689a!

[micahmo]

Added trimming to showInputDialog to disable the button when there's empty strings, and added trimming to keywords in eff689a!

Nice! We can try to add something similar to comment search at some point.