Auto-resize frames

Context: https://github.com/Automattic/compare-snapshot-tool/pull/7#issuecomment-1405833737

The frames that display the webpages don't seem to respond to window resizing. For example, if the window is resized smaller, the frames don't allow the user to horizontally scroll to reveal parts of the webpage that are out of view and don't resize after clicking the Reload button either. Also, if the window is resized larger, the frames don't utilize the extra space even after clicking the Reload button.

It happens in both snapshot and non-snapshot mode, but in non-snapshot mode, changing the device/viewport will refresh the frames to the current widow width. I have a feeling that the complexity of what's going on behind the scenes would make this hard to implement, but I just wanted to mention it!

Start by tracing how the snapshot and non-snapshot modes render webpage frames and how the Reload button and device/viewport changes refresh them. Reproduce the issue by resizing the window smaller and larger, then verify that frames resize, expose horizontally clipped content, and use newly available space without requiring an unrelated viewport change.

Written by the indexing model from the issue text.