fix: Export session API

[lforst]

We missed exporting the top-level session APIs.

[github-actions]

size-limit report 📦

Path	Size
@sentry/browser (incl. Tracing, Replay, Feedback) - Webpack (gzipped)	77.89 KB (0%)
@sentry/browser (incl. Tracing, Replay) - Webpack (gzipped)	69.17 KB (0%)
@sentry/browser (incl. Tracing, Replay with Canvas) - Webpack (gzipped)	73.1 KB (0%)
@sentry/browser (incl. Tracing, Replay) - Webpack with treeshaking flags (gzipped)	62.75 KB (0%)
@sentry/browser (incl. Tracing) - Webpack (gzipped)	33.36 KB (0%)
@sentry/browser (incl. browserTracingIntegration) - Webpack (gzipped)	33.26 KB (0%)
@sentry/browser (incl. Feedback) - Webpack (gzipped)	31.23 KB (0%)
@sentry/browser (incl. sendFeedback) - Webpack (gzipped)	31.24 KB (0%)
@sentry/browser - Webpack (gzipped)	22.49 KB (0%)
@sentry/browser (incl. Tracing, Replay, Feedback) - ES6 CDN Bundle (gzipped)	76.28 KB (+0.03% 🔺)
@sentry/browser (incl. Tracing, Replay) - ES6 CDN Bundle (gzipped)	67.78 KB (+0.03% 🔺)
@sentry/browser (incl. Tracing) - ES6 CDN Bundle (gzipped)	33.71 KB (+0.06% 🔺)
@sentry/browser - ES6 CDN Bundle (gzipped)	24.82 KB (+0.08% 🔺)
@sentry/browser (incl. Tracing, Replay) - ES6 CDN Bundle (minified & uncompressed)	213.24 KB (+0.03% 🔺)
@sentry/browser (incl. Tracing) - ES6 CDN Bundle (minified & uncompressed)	101.86 KB (+0.06% 🔺)
@sentry/browser - ES6 CDN Bundle (minified & uncompressed)	74.36 KB (+0.08% 🔺)
@sentry/browser (incl. Tracing) - ES5 CDN Bundle (gzipped)	36.96 KB (+0.05% 🔺)
@sentry/react (incl. Tracing, Replay) - Webpack (gzipped)	69.49 KB (0%)
@sentry/react - Webpack (gzipped)	22.52 KB (0%)
@sentry/nextjs Client (incl. Tracing, Replay) - Webpack (gzipped)	86.98 KB (0%)
@sentry/nextjs Client - Webpack (gzipped)	50.19 KB (0%)
@sentry-internal/feedback - Webpack (gzipped)	17.22 KB (0%)