build: improve WASM webui performance

[adamdecaf]

The webui built with fyne is slow on some browsers. This is a known issue within fyne as it paints a big <canvas> element (that looks identical to desktop GUIs).

This is a known issue with Fyne, see fyne-io/fyne#2803, fyne-io/fyne#5216

Possible Solutions

• Shrink the wasm bundle by removing deadcode
  • Locally I tried using wasm-opt to prune deadcode but Go's stdlib is still fairly large.
  • An alternative / solution is being discussed for Go
• Simplify the webui interface (fewer nested elements, less callback and animations)

[adamdecaf]

Using wasm-opt on a ui.wasm file took 20mins on my system for a 3MB reduction in size. The UI performance didn't improve enough to introduce the additional 20min build time.

[adamdecaf]

Fyne seems to include some large data tables (for emojis and markdown parsing). Maybe these could be removed for WASM builds?

Markdown parsing with UTF-8 tables - https://github.com/yuin/goldmark