bump minimum to node 20

Author: devongovett

.github/workflows/ci.yml

@@ -61,7 +61,7 @@ jobs:
     name: Unit tests (${{ matrix.os }}, Node ${{ matrix.node }})
     strategy:
       matrix:
-        node: [18, 20]
+        node: [20, 22]
         os: [ubuntu-latest, macos-latest, windows-latest]
     runs-on: ${{ matrix.os }}
     steps:
@@ -96,7 +96,7 @@ jobs:
     name: Integration tests (${{ matrix.os }}, Node ${{ matrix.node }})
     strategy:
       matrix:
-        node: [18, 20]
+        node: [20, 22]
         os: [ubuntu-latest, macos-latest, windows-latest]
       # These tend to be quite flakey, so one failed instance shouldn't stop
       # others from potentially succeeding