feat: add html payment pages for browser 402 responses

[tmm]

Experimental: Renders 402 as html in browsers with way to complete payment (~universal payment links).

Try it out

gh pr checkout 220
cp .env.example .env # set MPP_SECRET_KEY
pnpm i
pnpm dev:example charge # open `http://localhost:5173/api/photo` in your browser

For Stripe example, set VITE_STRIPE_PUBLIC_KEY and VITE_STRIPE_SECRET_KEY and run pnpm dev:example stripe, the open http://localhost:5173/api/fortune in your browser.

Examples

tempo.charge()

005788_Firefox_2026-03-23-19.13.47.mp4

stripe.charge()

005801_Firefox_2026-03-23-19.34.36.mp4

TODO

• add browser tests to make sure script tags don't regress
• different approach to html rendering?
• customization (html styles, stripe elements options, etc.)

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/mppx@220

commit: f572e5f