Search bar: add ❌ button to clear the search terms; emit actions upon user input.

[tyreseluo]

Partially addresses #123.

[kevinaboos]

I'm confused by a few things in this PR.

1. What is the purpose of this PR? there's no description, and the title is lengthy but not quite detailed enough.
2. As a follow-up to the above, this doesn't seem to actually implement the search functionality. So it'd be pretty confusing for users to see a new search bar that they can interact with but doesn't actually do anything.... unless there is another PR that is designed as a pairing to this?
3. The search timer idea is unusual, to say the least. The action of searching should happen automatically upon typing (i.e., when the typed text changes), which you can determine by checking for actions on the actual TextInput widget.

[tyreseluo]

That's my problem I didn't describe it clearly, I meant an enhancement to the search bar component. Add Action and clicked events and close icon.

[tyreseluo]

For the room search issue #123, I separated it and will be submitting a new PR. As you mentioned in PR #212 , turn some big PRs into some small ones.

[kevinaboos]

ok nice, now I understand what the scope of this PR is. It looks good, just one small nit about unnecessary changes to the rooms_sidebar.rs file.