Develop frontend for creating announcements

[KathleenX7]

Notion ticket link

Develop frontend for creating announcements

Implementation description

• Add room button creates a new tab with greyed out title "New Announcement"
• Clicking on the new tab brings up a different right panel. There is a + button where you can add and remove Rooms
• Adding rooms will change the title of the tab from "New Announcement" to a list of rooms
• Pressing post with rooms defined and text in the text box will remove the new announcement

Steps to test

1. Click add room button
2. Click on New Announcements tab
3. Try adding and removing rooms (tab title will also change)
4. Add text in "Type an announcement..." and press post. This should delete the new tab.

What should reviewers focus on?

Checklist

• My PR name is descriptive and in imperative tense
• My commit messages are descriptive and in imperative tense. My commits are atomic and trivial commits are squashed or fixup'd into non-trivial commits
• I have run the appropriate linter(s)
• I have requested a review from the PL, as well as other devs who have background knowledge on this PR or who will be building on top of this PR