fix: pin all GitHub Actions to full commit SHAs (resolves SonarCloud S7637) (#90)

Pin all floating version tags (@v1, @v2, @v3, @v4, @master) to full commit
SHAs across all workflow files to eliminate supply chain security risk.

Actions pinned:
- actions/checkout@v3 -> f43a0e5 (v3.6.0) in release.yml, sync-wiki.yml
- actions/checkout@v4 -> 34e1148 (v4) in tests.yml
- shivammathur/setup-php@v2 -> accd612 (v2) in all workflows
- actions/setup-node@v4 -> 49933ea (v4) in playground-tests*.yml, wordpress-tests.yml
- actions/upload-artifact@v4 -> ea165f8 (v4) in playground-tests*.yml, wordpress-tests.yml
- softprops/action-gh-release@v1 -> de2c0eb (v1) in release.yml
- codacy/codacy-analysis-cli-action@v4 -> 562ee3e (v4) in code-quality.yml
- github/codeql-action/upload-sarif@v3 -> 603b797 (v3) in code-quality.yml
- swissspidy/wp-performance-action@v2.0.3 -> b7e3ffc (v2.0.3) in playground-tests.yml
- SonarSource/sonarqube-scan-action@master -> 9598b8a in sonarcloud.yml

Closes #89

.github/workflows/playground-tests.yml

@@ -40,7 +40,7 @@ jobs:
     - uses: actions/checkout@692973e3d937129bcbf40652eb9f2f61becf3332 # v4.1.7
 
     - name: Setup Node.js
-      uses: actions/setup-node@v4
+      uses: actions/setup-node@49933ea5288caeca8642d1e84afbd3f7d6820020 # v4
       with:
         node-version: ${{ matrix.node-version }}
         cache: 'npm'
@@ -67,7 +67,7 @@ jobs:
     - uses: actions/checkout@692973e3d937129bcbf40652eb9f2f61becf3332 # v4.1.7
 
     - name: Setup Node.js
-      uses: actions/setup-node@v4
+      uses: actions/setup-node@49933ea5288caeca8642d1e84afbd3f7d6820020 # v4
       with:
         node-version: '20'
         cache: 'npm'
@@ -142,7 +142,7 @@ jobs:
 
     - name: Upload Cypress artifacts
       if: always()
-      uses: actions/upload-artifact@v4
+      uses: actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02 # v4
       with:
         name: cypress-single-site-results
         path: |
@@ -163,7 +163,7 @@ jobs:
     - uses: actions/checkout@692973e3d937129bcbf40652eb9f2f61becf3332 # v4.1.7
 
     - name: Setup Node.js
-      uses: actions/setup-node@v4
+      uses: actions/setup-node@49933ea5288caeca8642d1e84afbd3f7d6820020 # v4
       with:
         node-version: '20'
         cache: 'npm'
@@ -239,7 +239,7 @@ jobs:
 
     - name: Upload Cypress artifacts
       if: always()
-      uses: actions/upload-artifact@v4
+      uses: actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02 # v4
       with:
         name: cypress-multisite-results
         path: |
@@ -261,7 +261,7 @@ jobs:
     - uses: actions/checkout@692973e3d937129bcbf40652eb9f2f61becf3332 # v4.1.7
 
     - name: WordPress Performance Tests
-      uses: swissspidy/wp-performance-action@v2.0.3
+      uses: swissspidy/wp-performance-action@b7e3ffcf0fc4a48b62492e021e0ebeb51430ff11 # v2.0.3
       with:
         plugins: |
           ./