add migration steps from v2 to v3 (#32)

.changeset/olive-chairs-grab.md

@@ -2,9 +2,21 @@
 '@vercel/flags': minor
 ---
 
-@vercel/flags/next: Export `dedupe` function
+**BREAKING CHANGES**
 
-`dedupe` is a middleware-friendly version of `React.cache`. It allows ensuring a function only ever runs once for a request.
+- removed all `unstable_` prefixes, e.g. `unstable_flag` is now `flag`
+- removed `getPrecomputationContext`, use `dedupe` instead (see below)
+- moved all provider functions to dedicated packages
+  - `@vercel/flags/providers/launchdarkly` → `@flags-sdk/launchdarkly`
+  - `@vercel/flags/providers/statsig` → `@flags-sdk/statsig`
+  - `@vercel/flags/providers/split` → `@flags-sdk/split`
+  - `@vercel/flags/providers/hypertune` → `@flags-sdk/hypertune`
+  - `@vercel/flags/providers/optimizely` → `@flags-sdk/optimizely`
+  - `@vercel/flags/providers/happykit` → `@flags-sdk/happykit`
+
+**@vercel/flags/next: Added a `dedupe` function**
+
+`dedupe` is a middleware-friendly version of `React.cache`. It allows ensuring a function only ever runs once per request.
 
 ```ts
 import { dedupe } from '@vercel/flags/next';