build: add Node 16 and 18 to the CI matrix

Update documentation, so that it does not become outdated whenever a new version of Node is released.

Test on the current version of Node, so we can spot problems early, but don't claim to support it as current release line sometimes introduces bugs, which are later fixed by Node itself.

Fixes karma-runner#3728

.github/workflows/test.yml

@@ -20,7 +20,7 @@ jobs:
           fetch-depth: 0
       - uses: actions/setup-node@v2
         with:
-          node-version: 14
+          node-version: 16
           cache: npm
       - run: npm ci
       - run: npm run build:check
@@ -33,7 +33,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        node: [10, 12]
+        node: [10, 12, 14, 18]
     steps:
       - uses: actions/checkout@v2
       - uses: actions/setup-node@v2
@@ -48,7 +48,7 @@ jobs:
     runs-on: windows-latest
     strategy:
       matrix:
-        node: [10, 12, 14]
+        node: [10, 12, 14, 16, 18]
     steps:
       - uses: actions/checkout@v2
       - uses: actions/setup-node@v2

docs/intro/01-installation.md

@@ -5,7 +5,7 @@ Karma runs on [Node.js] and is available as an [npm] package.
 On Mac or Linux we recommend using [NVM](https://github.com/creationix/nvm). On Windows, download Node.js
 from [the official site](https://nodejs.org/) or use the [NVM PowerShell Module](https://www.powershellgallery.com/packages/nvm).
 
-Note: Karma currently works on Node.js **6.x**, **8.x**, and **10.x**. See [FAQ] for more info.
+Karma works on any [supported LTS releases](https://nodejs.org/en/about/releases/) of Node.js.
 
 ## Installing Karma and plugins