docs: add migration guide

Author: gagik

packages/mongodb-downloader/README.md

@@ -0,0 +1,39 @@
+## mongodb-downloader
+
+A simple library to download MongoDB binaries for different platforms and versions.
+
+### Migrating from v0.4 to v0.5
+
+In v0.5.x, the library introduced lockfiles to prevent parallel downloads of the same MongoDB binary. It also changed the arguments for the `downloadMongoDb` and `downloadMongoDbWithVersionInfo` functions, introducing a new `useLockfile` field and using a single options object instead of separate parameters for different options. It is recommended to enable lockfiles to prevent redundant downloads unless you have a specific reason not to.
+
+```ts
+// Before (v0.4.x)
+downloadMongoDb('/tmp/directory', '4.4.6', {
+  platform: 'linux',
+  arch: 'x64',
+});
+
+downloadMongoDbWithVersionInfo('/tmp/directory', '4.4.6', {
+  arch: 'x64',
+});
+
+// After (v0.5.x)
+downloadMongoDb({
+  downloadDir: '/tmp/directory',
+  version: '4.4.6',
+  useLockfile: true, // New, required field.
+  downloadOptions: {
+    platform: 'linux',
+    arch: 'x64',
+  },
+});
+
+downloadMongoDbWithVersionInfo({
+  downloadDir: '/tmp/directory',
+  version: '4.4.6',
+  useLockfile: true, // New, required field.
+  downloadOptions: {
+    arch: 'x64',
+  },
+});
+```