CI: cache npm packages between runs

Every android-test and ios-test job runs "npm install" from scratch,
re-downloading the full dependency tree on every run. Cache ~/.npm
keyed on package-lock.json and test/test.ts (whose changes can alter
installed test-app dependencies), with an OS-scoped restore-key
fallback for partial hits.

Author: ofalvai

.github/workflows/ci-test.yml

@@ -37,6 +37,15 @@ jobs:
 
       - uses: jdx/mise-action@v4
 
+      - name: Cache npm packages
+        uses: actions/cache@v6
+        with:
+          path: ~/.npm
+          # Note about test.ts: some NPM package versions are hardcoded here and installed during the test run.
+          key: ${{ runner.os }}-npm-${{ hashFiles('package-lock.json', 'test/test.ts') }}
+          restore-keys: |
+            ${{ runner.os }}-npm-
+
       - name: Install dependencies
         run: npm install
 
@@ -76,6 +85,15 @@ jobs:
 
       - uses: jdx/mise-action@v4
 
+      - name: Cache npm packages
+        uses: actions/cache@v6
+        with:
+          path: ~/.npm
+          # Note about test.ts: some NPM package versions are hardcoded here and installed during the test run.
+          key: ${{ runner.os }}-npm-${{ hashFiles('package-lock.json', 'test/test.ts') }}
+          restore-keys: |
+            ${{ runner.os }}-npm-
+
       - name: Run iOS Tests
         run: |
           npm install