chore: add migration guide (#4)

MIGRATING.md

@@ -0,0 +1,43 @@
+# Migrating to @aws-cdk-containers/ecs-service-extensions v2
+
+The v2 version of this module comes with two main changes. It is now
+compatible with CDK v2, and has multi-language support. It is recommended
+that you migrate your own application or construct library to v2 of
+`@aws-cdk-containers/ecs-service-extensions` to continue to receive
+features and bug fixes.
+
+There are no big API changes between v1 and v2. However, there may be
+some small modifications necessary to get your application ready for
+`@aws-cdk-containers/ecs-service-extensions` v2.
+
+## Step 1: Migrate your CDK application or library to AWS CDK v2
+
+See the steps [here](https://docs.aws.amazon.com/cdk/v2/guide/migrating-v2.html).
+
+## Step 2: Update dependencies in your package.json
+
+```json
+{
+  "dependencies": {
+    "@aws-cdk-containers/ecs-service-extensions": "^2.0.0",
+  }
+}
+```
+
+## Step 3: Type Changes
+
+If you use any of the following properties, change them to use their v2 types.
+
+- `Environment.cluster` changes from type `ecs.Cluster` to `ecs.ICluster`.
+- `InjecterExtensionProps.injectables` changes from type `Injectable[]` to `IInjectable[]`.
+- `MeshProps.protocol` changes from type `appmesh.Protocol` to `Protocol`.
+
+## Step 4: Name Changes
+
+If you use any of the following APIs, change them to use their v2 names.
+
+| v1 API                              | v2 API
+|-------------------------------------|------------------------------------------------|
+| `ConnectToProps.local_bind_port`    | `ConnectToProps.localBindPort`                 |
+| `Injectable`                        | `IInjectable`                                  |
+| `GrantInjectable`                   | `IGrantInjectable`                             |

README.md

@@ -23,9 +23,14 @@ import {
   Service,
   ServiceDescription,
   XRayExtension,
-} from 'cdk-ecs-service-extensions';
+} from '@aws-cdk-containers/ecs-service-extensions';
 ```
 
+If you are using the `@aws-cdk-containers/ecs-service-extensions` v1 and need to migrate to
+v2, see the [Migration Guide](https://github.com/cdklabs/cdk-ecs-service-extensions/blob/main/MIGRATING.md).
+
+## `Service` construct
+
 The `Service` construct provided by this module can be extended with optional `ServiceExtension` classes that add supplemental ECS features including:
 
 - [AWS X-Ray](https://aws.amazon.com/xray/) for tracing your application