feat(lambda): nodejs14.x runtime (#12861)

Blog post: [Node.js 14.x runtime now available in AWS Lambda](https://aws.amazon.com/blogs/compute/node-js-14-x-runtime-now-available-in-aws-lambda/)
Developer Guide: [Node.js lambda runtimes](https://docs.aws.amazon.com/lambda/latest/dg/lambda-runtimes.html)

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*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

packages/@aws-cdk/aws-lambda/lib/runtime.ts

@@ -78,6 +78,11 @@ export class Runtime {
    */
   public static readonly NODEJS_12_X = new Runtime('nodejs12.x', RuntimeFamily.NODEJS, { supportsInlineCode: true });
 
+  /**
+   * The NodeJS 14.x runtime (nodejs14.x)
+   */
+  public static readonly NODEJS_14_X = new Runtime('nodejs14.x', RuntimeFamily.NODEJS, { supportsInlineCode: false });
+
   /**
    * The Python 2.7 runtime (python2.7)
    */