fix: upgrade to node 21

Author: BenedictLang

.github/workflows/checks.yml

@@ -8,7 +8,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        node-version: [18.x]
+        node-version: [21.x]
     steps:
       - uses: actions/checkout@v2
 
@@ -29,13 +29,13 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        node-version: [16.x, 18.x]
+        node-version: [20.x, 21.x]
     steps:
       - uses: actions/checkout@v2
 
       - uses: pnpm/action-setup@v2
         with:
-          version: 8
+          version: 9
 
       - uses: actions/setup-node@v2
         with: