[docs] Update the NodeJS version policy

This version policy is a migration from tracker issues.

I have also taken the opportunity to tidy this up, and update it in line
with the version policy changes introduced in IDEA-168.

general/development/policies/node.md

@@ -0,0 +1,79 @@
+---
+title: NodeJS
+sidebar_label: NodeJS versions
+description: Information about how NodeJS supported versions correlate with Moodle releases and the policy controlling it.
+tags:
+  - Requirements
+  - Support
+  - Releases
+  - NodeJS
+---
+
+New LTS NodeJS versions are [released every 12 months](https://github.com/nodejs/release#release-schedule) and supported for three years. Moodle tries to ensure a compromise between support and churn by ensuring that the version of NodeJS in use is supported at all times.
+
+## Policy statement
+
+### NodeJS
+
+<Since versions={["3.1"]} issueNumber="MDL-63346" />
+
+1. This policy will be applied to _all_ supported branches, including stable and security-only releases.
+1. This policy does not require that any tool be updated, unless strictly needed by nodejs/npm or its own dependencies/changes
+1. It won't include npm audit changes either. Those are handled separately.
+1. Normally, only changes to `.nvmrc` and `package.json` will happen.
+1. Changes to project dependencies should be handled in a separate issue.
+
+### Project Dependencies
+
+<Since versions={["5.0"]} issueNumber="IDEA-168" />
+
+  1. To avoid impact to the community, dependency updates which impact built output should be kept to a minimum.
+  1. Dependency updates should be backported to the first Major release in a Series, for example Moodle 5.0.
+
+## Upgrade guidelines
+
+### NodeJS
+
+To update the NodeJS version required, the following approach is typically recommended:
+
+1. Update the `.nvmrc` file to reflect the `lts/[name]` of the new LTS version
+1. Update the `package.json` to set the `engines` for the new restiction in the format: `>= [new version] < [next version]`, for example:
+
+    ```json
+    "engines": {
+       "node": ">=20.11.0 <21"
+    }
+    ```
+
+1. Install the new NodeJS version:
+
+    ```sh
+    nvm install && nvm use
+    ```
+
+1. Update the NodeJS dependencies with the new version of NodeJS:
+
+    ```sh
+    rm -rf node_modules
+    npm install
+    ```
+
+1. Verify the update:
+
+    ```sh
+    npx grunt
+    npx grunt jsdoc
+    ```
+
+In most situations there will be no issues here and changes can be committed and backported to all stable and security-supported branches.
+
+#### Troubleshooting
+
+Where a project dependency is no longer supported due to the new version of NodeJS, it may be necessary to upgrade the dependency.
+
+### Project dependencies
+
+The following tooling may be useful for the purposes of updating the project dependencies:
+
+- `npm outdated`
+- `npm audit`