add migration guide back in and add to fernignore

Author: zplata

.fernignore

@@ -1,6 +1,7 @@
 # Specify files that shouldn't be modified by Fern
 
 README.md
+MIGRATION.md
 
 # Oauth Helpers
 src/api/types/OAuthScope.ts

MIGRATION.md

@@ -0,0 +1,54 @@
+# Migration
+
+When migrating to a new major version of this SDK, please consult the notes here for breaking changes, new features, and related fixes.
+
+## v2.x.x -> v3.0.0
+
+There are a few breaking changes with v3.0.0 of the Webflow JS SDK. Please see the `Breaking` section below for more details and consult our [API Docs](https://developers.webflow.com/data/reference/rest-introduction) for examples of usage.
+
+### Breaking
+
+#### CMS APIs
+
+- **CHANGED**: Deleting a Collection is now achieved through `client.collections.delete()`, which was previously an API used to delete a Collection field.
+    - To delete a Collection, use `client.collections.delete()`
+        - e.g., `client.collections.delete(collectionId)`
+    - **NEW**: To delete a Collection field, use `client.collections.fields.delete()`
+        - e.g., `client.collections.fields.delete(collectionId, fieldId)`
+    - **REMOVED**: `client.collections.deleteCollection()` 
+- **CHANGED**: Creating bulk CMS Items in multiple locales is now achieved through `client.collections.createItems()`
+    - e.g.,
+    ```ts
+        const newItems = client.collections.items.createItems(collectionId, {
+            cmsLocaleIds: [primaryCmsLocaleId, secondaryCmsLocaleId],
+            isArchived: false,
+            isDraft: false,
+            fieldData: {
+                name: "My Item For Multiple Locales",
+                slug: "my-item",
+                "plain-text": "foo",
+            },
+        });
+    ```
+    - **REMOVED**: `client.collections.createItemForMultipleLocales()`
+
+#### Pages APIs
+
+- **CHANGED**: The `locale` query parameter is now `localeId`
+    - e.g., `client.pages.list(siteId, { localeId: "65427cf400e02b306eaa04a0" })`
+
+### New Features
+
+#### CMS APIs
+
+- **NEW**: Bulk CMS Item API support, with the ability to specify one or many locales to manage the CMS Item in. See [docs](https://developers.webflow.com/data/reference/cms/collection-items/bulk-items/create-items) for more on usage.
+    - `collections.items.createItems()` - Create a single CMS Item or multiple CMS Items in a Collection
+    - `collections.items.updateItems()` - Update multiple CMS Item(s) in a Collection
+    - `collections.items.updateItemsLive()` - Update multiple live CMS Item(s) in a Collection
+    - `collections.items.deleteItems()` - Unpublish/delete multiple CMS Item(s) in a Collection
+    - `collections.items.deleteItemsLive()` - Unpublish/delete multiple live CMS Item(s) in a Colllection
+
+### Fixes
+
+- Some APIs that created resources (i.e. `collections.items.createItem()`) had request payload types that required an `id`, which is not possible to provide. This is no longer required.
+- `fieldData` type in CMS Items now allows arbitrary extra key/value pairs