chore: update node version in readme (aws#18144)

fixes: aws#18130 

----

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

CONTRIBUTING.md

@@ -52,7 +52,7 @@ See [Gitpod section](#gitpod) on how to set up the CDK repo on Gitpod.
 
 The following tools need to be installed on your system prior to installing the CDK:
 
-- [Node.js >= 10.13.0](https://nodejs.org/download/release/latest-v10.x/)
+- [Node.js >= 14.15.0](https://nodejs.org/download/release/latest-v14.x/)
   - We recommend using a version in [Active LTS](https://nodejs.org/en/about/releases/)
   - ⚠️ versions `13.0.0` to `13.6.0` are not supported due to compatibility issues with our dependencies.
 - [Yarn >= 1.19.1, < 2](https://yarnpkg.com/lang/en/docs/install)

README.md

@@ -19,7 +19,7 @@ infrastructure definition and share it without worrying about boilerplate logic.
 
 The CDK is available in the following languages:
 
-* JavaScript, TypeScript ([Node.js ≥ 10.13.0](https://nodejs.org/download/release/latest-v10.x/))
+* JavaScript, TypeScript ([Node.js ≥ 14.15.0](https://nodejs.org/download/release/latest-v14.x/))
   - We recommend using a version in [Active LTS](https://nodejs.org/en/about/releases/)
   - ⚠️ versions `13.0.0` to `13.6.0` are not supported due to compatibility issues with our dependencies.
 * Python ([Python ≥ 3.6](https://www.python.org/downloads/))
@@ -77,7 +77,7 @@ in the CDK Developer Guide.
 For a detailed walkthrough, see the [tutorial](https://docs.aws.amazon.com/cdk/latest/guide/getting_started.html#hello_world_tutorial) in the AWS CDK [Developer Guide](https://docs.aws.amazon.com/cdk/latest/guide/home.html).
 
 ### At a glance
-Install or update the [AWS CDK CLI] from npm (requires [Node.js ≥ 10.13.0](https://nodejs.org/download/release/latest-v10.x/)). We recommend using a version in [Active LTS](https://nodejs.org/en/about/releases/)
+Install or update the [AWS CDK CLI] from npm (requires [Node.js ≥ 14.15.0](https://nodejs.org/download/release/latest-v14.x/)). We recommend using a version in [Active LTS](https://nodejs.org/en/about/releases/)
 ⚠️ versions `13.0.0` to `13.6.0` are not supported due to compatibility issues with our dependencies.
 
 ```console