chore: Better documentation of ARM64 usage (#245)

Fix #243

README.md

@@ -175,7 +175,7 @@ const myProvider = new FargateRunnerProvider(this, 'fargate runner', {
   label: 'customized-windows-fargate',
   vpc: vpc,
   securityGroup: runnerSg,
-  imageBuiler: myWindowsBuilder,
+  imageBuidler: myWindowsBuilder,
 });
 
 // create the runner infrastructure
@@ -184,6 +184,23 @@ new GitHubRunners(stack, 'runners', {
 });
 ```
 
+The runner OS and architecture is determined by the image it is set to use. For example, to create a CodeBuild runner provider for ARM64 set the `architecture` property for the image builder to `Architecture.ARM64` and use the `LINUX_ARM64_DOCKERFILE_PATH` constant.
+
+```typescript
+new GitHubRunners(stack, 'runners', {
+   providers: [
+      new FargateRunnerProvider(this, 'fargate runner', {
+         labels: ['arm64', 'fargate'],
+         imageBuidler: new CodeBuildImageBuilder(this, 'image builder', {
+            architecture: Architecture.ARM64,
+            os: Os.LINUX,
+            dockerfilePath: FargateRunner.LINUX_ARM64_DOCKERFILE_PATH,
+         }),
+      }),
+   ],
+});
+```
+
 ## Architecture
 
 ![Architecture diagram](architecture.svg)

src/providers/codebuild.ts

@@ -31,6 +31,8 @@ export interface CodeBuildRunnerProviderProps extends RunnerProviderProps {
   /**
    * Image builder for CodeBuild image with GitHub runner pre-configured. A user named `runner` is expected to exist with access to Docker-in-Docker.
    *
+   * The image builder determines the OS and architecture of the runner.
+   *
    * @default image builder with `CodeBuildRunner.LINUX_X64_DOCKERFILE_PATH` as Dockerfile
    */
   readonly imageBuilder?: IImageBuilder;

src/providers/ec2.ts

@@ -133,6 +133,8 @@ export interface Ec2RunnerProviderProps extends RunnerProviderProps {
   /**
    * AMI builder that creates AMIs with GitHub runner pre-configured. On Linux, a user named `runner` is expected to exist with access to Docker.
    *
+   * The AMI builder determines the OS and architecture of the runner.
+   *
    * @default AMI builder for Ubuntu Linux on the same subnet as configured by {@link vpc} and {@link subnetSelection}
    */
   readonly amiBuilder?: IAmiBuilder;

src/providers/fargate.ts

@@ -32,6 +32,8 @@ export interface FargateRunnerProviderProps extends RunnerProviderProps {
   /**
    * Provider running an image to run inside CodeBuild with GitHub runner pre-configured. A user named `runner` is expected to exist.
    *
+   * The image builder determines the OS and architecture of the runner.
+   *
    * @default image builder with `FargateRunner.LINUX_X64_DOCKERFILE_PATH` as Dockerfile
    */
   readonly imageBuilder?: IImageBuilder;

src/providers/lambda.ts

@@ -34,6 +34,8 @@ export interface LambdaRunnerProviderProps extends RunnerProviderProps {
    *
    * The default command (`CMD`) should be `["runner.handler"]` which points to an included `runner.js` with a function named `handler`. The function should start the GitHub runner.
    *
+   * The image builder determines the OS and architecture of the runner.
+   *
    * @see https://github.com/CloudSnorkel/cdk-github-runners/tree/main/src/providers/docker-images/lambda
    * @default image builder with LambdaRunner.LINUX_X64_DOCKERFILE_PATH as Dockerfile
    */