BUG: UI: Managing of validators on HiDPI screen requires workarounds

[pepawel]

Describe the bug When using HiDPI screen (3840x2160 resolution with 200% scaling) UI in "Staking" tab doesn't work well. The button to add validator key doesn't respond to click.

To Reproduce Steps to reproduce the behavior:

1. Go to "Staking" tab.
2. Observe elements near the button at the bottom are misplaced.
3. Click "CLICK OR DRAG TO INSERT KEY" button.
4. Observe nothing happens.

Expected behavior File selector should appear.

Desktop:

• OS: Pop!_OS Linux
• Screen resolution: 3840x2160
• Scaling factor: 200%
• Launcher version: 2.0-RC2

Node:

• OS: Ubuntu 20.04
• Affected service: Lighthouse

Additional context When I decrease the height of the Stereum window to 1/2 of screen height, the issue disappears and the UI starts to work.