feat(solidstart): Add sentry onBeforeResponse middleware to enable distributed tracing

[andreiborza]

Works by adding the Sentry middlware to your src/middleware.ts file:

import { sentryBeforeResponseMiddleware } from '@sentry/solidstart/middleware';
import { createMiddleware } from '@solidjs/start/middleware';

export default createMiddleware({
  onBeforeResponse: [
    sentryBeforeResponseMiddleware(),
    // Add your other middleware handlers after `sentryBeforeResponseMiddleware`
  ],
});

And specifying ./src/middleware.ts in app.config.ts

Closes: #12551

[s1gr1d]

LGTM