docs(flags): add index flag docs for javascript

docs/platforms/javascript/common/feature-flags/index.mdx

@@ -0,0 +1,44 @@
+---
+title: Set Up Feature Flags
+sidebar_order: 7000
+notSupported:
+  - javascript.aws-lambda
+  - javascript.azure-functions
+  - javascript.bun
+  - javascript.capacitor
+  - javascript.cloudflare
+  - javascript.connect
+  - javascript.cordova
+  - javascript.deno
+  - javascript.electron
+  - javascript.express
+  - javascript.fastify
+  - javascript.gcp-functions
+  - javascript.hapi
+  - javascript.koa
+  - javascript.nestjs
+  - javascript.nodejs
+  - javascript.wasm
+description: With Feature Flags, Sentry tracks flag evaluations in your application and reports their state on error. Sentry will also record an audit log of feature flag changes and report any suspicious changes that may have triggered an error.
+---
+
+<Alert level="info" title="Currently in Beta">
+
+**Feature flag change tracking** and **feature flag evaluation tracking** is currently in closed beta. If you'd like to be added to the beta, please fill out [this form](https://forms.gle/EeNwTepvVwt7poAJ8).
+
+</Alert>
+
+## Prerequisites
+
+* You have the <PlatformLink to="/">Javascript SDK installed</PlatformLink> (version 8.41.0-beta.0 or higher).
+
+## Enable Evaluation Tracking
+
+Evaluation tracking requires enabling an SDK integration. Integrations are provider specific. Documentation for supported providers is listed below.
+
+- [OpenFeature](/platforms/javascript/integrations/openfeature/)
+- [LaunchDarkly](/platforms/javascript/integrations/launchdarkly/)
+
+## Enable Change Tracking
+
+Change tracking requires registering a Sentry webhook with your feature flag provider. Set up varies by provider and is documented in detail [here](/product/explore/feature-flags/#set-up-your-integration-specific-webhook).