chore: document how to add support for a new node major versions (#4590)

Resolves #4581

---

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

[Apache 2.0 license]: https://www.apache.org/licenses/LICENSE-2.0

CONTRIBUTING.md

@@ -240,3 +240,22 @@ be released after a last validation build.
 
 The latest release information (for both of the Docker image tags) can be seen
 on [ECR Public Gallery](https://gallery.ecr.aws/jsii/superchain)
+
+## Support for new Node Major versions
+
+When a new major version of node is released, we need to update the `@jsii/check-node` package.
+This package is responsible for identifiying which node version is being used by the current process,
+whether or not it is supported and tested, and produces appropriate warnings in case it isnt.
+
+> Note that `jsii` will execute on every node version, so "adding support" here only means supressing or showing
+> warnings that inform the user on the level of support it has.
+
+### Steps
+
+1. Add a `new NodeRelease(...)` to [constants.ts](./packages/@jsii/check-node/src/constants.ts)
+2. If its an LTS version, add the new node version to our testing matrix in [main.yml](./.github/workflows/main.yml) and [docker-images.yml](./.github/workflows/docker-images.yml).
+
+### Useful Resources
+
+- [https://endoflife.date/nodejs](https://endoflife.date/nodejs)
+- [Adding support for node 22 PR](https://github.com/aws/jsii/pull/4489)

packages/@jsii/check-node/src/constants.ts

@@ -45,11 +45,11 @@ export class NodeRelease {
       untested: true,
     }),
     new NodeRelease(19, { endOfLife: new Date('2023-06-01'), untested: true }),
+    new NodeRelease(21, { endOfLife: new Date('2024-06-01'), untested: true }),
 
     // Currently active releases (as of last edit to this file...)
     new NodeRelease(18, { endOfLife: new Date('2025-04-30') }),
     new NodeRelease(20, { endOfLife: new Date('2026-04-30') }),
-    new NodeRelease(21, { endOfLife: new Date('2024-06-01'), untested: true }),
     new NodeRelease(22, { endOfLife: new Date('2027-04-30') }),
 
     // Future (planned releases)