Use tabular nums for count down for better alignment

[TimonVS]

Description

Before:

The count down "jumps" around a little bit every second because different numbers take up slightly more or slightly less space.

After:

font-variant-numeric: tabular-nums straightens out the difference, kind of like a monospace font does. The result is a bit wider, but consistent.

It will still jump when going from 10s to 9s because it drops a character:

Test process

• [ ] Test A
• [ ] Test B

Requirements to merge

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my own code
• [x] I have commented my code in hard-to-understand areas
• [x] My changes generate no new warnings
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] New and existing unit tests pass locally with my changes