fix(ci): use step to get PR number via `gh` CLI

.github/workflows/ui-tests.yaml

@@ -2,6 +2,9 @@ name: 'UI tests'
 
 on: push
 
+permissions:
+  pull_requests: read
+
 jobs:
   cache-dependencies:
     runs-on: ubuntu-latest
@@ -27,6 +30,11 @@ jobs:
     needs: cache-dependencies
     steps:
       - uses: actions/checkout@v2
+      - name: Get PR number
+        id: pull_request
+        run: echo "::set-output name=number::$(gh pr view --json number -q .number || echo "")"
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
       - uses: actions/setup-node@v2
         with:
           node-version: '18.x'
@@ -59,7 +67,7 @@ jobs:
             const fs = require('fs');
             const deploymentUrl = fs.readFileSync('_vercel-deployment-url', 'utf8');
             await github.rest.issues.createComment({
-              issue_number: context.issue.number,
+              issue_number: ${{ steps.pull_request.outputs.number }},
               owner: context.repo.owner,
               repo: context.repo.repo,
               body: `Deployed to ${deploymentUrl}`,