Add minimalist design

## Summary

The current design is a bit bulky - see example below where it covers a big part of the page:


## Motivation

The current design looks good on mobile but doesn't work too well in extension form. I feel as if having a smaller footprint by default would make it faster to quickly create issues. Especially in cases when you need to look at something on your current page for reference while making an issue.

## Describe alternatives you've considered

N/A

## Additional context

One possible mockup:


Stick with a very thin input field. This requires users to have a default repo selected.
Hitting enter within that field or clicking the paper airplane icon would submit the issue.

**What about label and other options?**
You could add a scroll handler that expands the popup a bit to reveal other input fields. Or have a triple dot button somewhere. Lots of creative ways to start small but still allow as much functionality as you want.

**What about Issueist branding?**
Again, lots of options. If you want "Issueist" somewhere in the default view: Maybe instead of a paper airplane icon, you have a full-width button below the input field labeled "Submit with Issueist". Otherwise, you can include it in any number of places when people expand to the advanced issue creation view noted above.

The issue names no files, tests, or entry points; begin by locating the extension's current popup design and comparing it with the supplied screenshots and mockup. Done means the default view has a smaller footprint while retaining issue submission and a way to reach additional options.

Written by the indexing model from the issue text.