Fix overflow

[ykiu]

What this PR does

This PR ensures the item search tool and the story builder render appropriately when their contents are long.

Before

The item search tool: when the search parameter list is long the search tool grows out of the viewport. The story builder: when there are many stories, the capture scene button at the bottom is pushed out of the viewport.

After

The item search tool: the search parameter list is now scrollable. The story builder: the capture scene button stays inside the viewport.

Test me

Start locally, then open the following link:

http://localhost:3001/#start=%7B%22initSources...%7D%5D%7D

Checklist

• [ ] There are unit tests to verify my changes are correct or unit tests aren't applicable (if so, write quick reason why unit tests don't exist)
  • No, because there's no testable changes.
• [ ] I've updated relevant documentation in doc/.
  • No, because there's nothing to document.
• [x] I've updated CHANGES.md with what I changed.
• [x] I've provided instructions in the PR description on how to test this PR.

[CLAassistant]

All committers have signed the CLA.

[ykiu]

@na9da Thank you for reviewing. I removed unused CSS classes.

I noticed the position of the story menu was off in my initial version, so I fixed it as well. The menu grows upwards/downwards depending on the space available, as it previously did:

Please verify it's not brokwn by using the following link:

http://localhost:3001/#start=%7B%22initSources...%7D%5D%7D

Thank you!