chore: release mpp@0.8.0

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0.8.0 (2026-03-25)

Minor Changes

• Added a Stripe Shared Payment Token (SPT) example demonstrating the full 402 → challenge → credential → retry flow using Stripe's payment method. Includes a server with SPT proxy endpoint and a headless client using a test card. (by @DerekCofausper, #145)
• Added Stripe payment method support (method="stripe", intent="charge") with client-side StripeProvider for SPT creation, server-side ChargeMethod for PaymentIntent verification, and Mpp::create_stripe() builder integration. Added stripe and integration-stripe feature flags backed by reqwest. (by @DerekCofausper, #145)

Patch Changes

• Fixed base64url_decode to accept standard base64 (+, /, = padding) in addition to URL-safe base64, following Postel's law and aligning with the mppx TypeScript SDK behavior. Added tests covering standard base64 with padding, URL-safe without padding, and standard alphabet without padding in both types.rs and headers.rs. (by @DerekCofausper, #145)