CI: run with Node v20 too 💚

back-port of 24ad611 to 5.x

Author: derhuerst

.github/workflows/test.yml

@@ -7,7 +7,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        node-version: [10.x, 12.x, 14.x, 16.x, 18.x]
+        node-version: [10.x, 12.x, 14.x, 16.x, 18.x, 20.x]
     steps:
     - name: checkout
       uses: actions/checkout@v4
@@ -25,7 +25,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        node-version: [10.x, 12.x, 14.x, 16.x, 18.x]
+        node-version: [10.x, 12.x, 14.x, 16.x, 18.x, 20.x]
     steps:
     - name: checkout
       uses: actions/checkout@v4