Improve WASM splash screen UX

[MartinZikmund]

What would you like to be added? 💡

The current WASM splash screen UX is a bit too plain and could use a few improvements:

• The progress bar should have same margin around it to avoid having it flush with the bottom of the window/screen, as it now seems like part of the browser UI instead of app's loading bar.
• The progress bar should be slightly taller to make it more visible and have rounded end caps
• The default color of the progress bar should not be red, as it feels like "error" state

Here is the current state for reference:

Why is this needed? 🤔

Improved UX

Renderer 🎨

• Skia
• Native

For which platforms 📱💻🖥️

WebAssembly

Anything else we need to know? 💬

No response