fix(ui): use percentages for content row container height

[a2937]

Summary of changes

This makes the height of the row container grow and shrink relative to the screen height rather than use fixed height when zoomed in. I also updated some of the units to be rem instead of px.

Checklist

• I have read and followed the contribution guidelines.
• I have read through the Code of Conduct and agree to abide by the rules.
• This PR is for one of the available issues and is not a PR for an issue already assigned to someone else.
• My PR title has a short descriptive name so the maintainers can get an idea of what the PR is about.
• I have provided a summary of my changes.

closes #1280

[shootermv]

@a2937 looks very nice!
question: have you tested the change on ubuntu operated machine?

[a2937]

The closest I have to Ubuntu is Windows Subsystem For Linux. I did not open up Firefox from it to test this PR yet though.

[shootermv]

May be better to ask @danielfriere-dev to take a look...