Optimize screen pushing by specifying CSS per screen/widget (no need to look...

Optimize screen pushing by specifying CSS per screen/widget (no need to look through every css file)

Measured TranferToAccount push time (since keypress to on_mount)

Before:
- 0.75s (first time)
- 0.45s
- 0.63s
- 0.53s

After:
- 0.55 (first time)
- 0.37s
- 0.36s
- 0.33s