test: Switch continuous integration to pnpm

Author: gwhitney

.github/workflows/ci.yaml

@@ -13,10 +13,13 @@ jobs:
               uses: actions/setup-node@v3
               with:
                   node-version: '18.x'
-            - name: Install dependencies
-              run: npm install
+            - name: Install pnpm and dependencies
+              uses: pnpm/action-setup@v2
+              with:
+                  version: latest
+                  run_install: true
             - name: Lint
-              run: npm run lint:check
+              run: pnpm lint:check
     test:
         runs-on: ubuntu-22.04
         steps:
@@ -29,7 +32,10 @@ jobs:
               uses: actions/setup-node@v3
               with:
                   node-version: '18.x'
-            - name: Install dependencies
-              run: npm install
+            - name: Install pnpm and dependencies
+              uses: pnpm/action-setup@v2
+              with:
+                  version: latest
+                  run_install: true
             - name: Test
-              run: npm run test:unit
+              run: pnpm test:unit