StackBlitz examples took **146+ seconds** to start due to heavy dev
dependencies
### Optimizations
- Eliminate heavy dev deps like `playwright (~200MB)` `@vitest/browser`
`vitest`
- Aggressive install flags: `--prefer-offline --reporter=silent
--ignore-scripts --no-optional`
- use pnpm
- Results **React example: 146s → ~25s (83% faster)**
- Add .stackblitzrc configuration file for StackBlitz environment setup
for
- Add prepare-stackblitz.js script to replace `workspace:*` dependencies
with "latest"
- Configure StackBlitz to run preparation script before installing
dependencies
- Change CSS import paths in examples from `@uppy/react/css/style.css`
to `@uppy/react/dist/styles.css` temporarily (will need to revert after
we release 5.0)
