feat: add expression functions demo workflow with various string checks and JSON parsing

Author: sgotluru

.github/workflows/expression-functions.yml

@@ -0,0 +1,48 @@
+name: Expression Functions Demo
+
+on:
+  push:
+    branches:
+      - main
+  issues:
+    types: [opened, labeled]
+
+jobs:
+  expression-functions:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check if string contains substring
+        if: contains('Hello world', 'llo')
+        run: echo "The string contains the substring."
+        
+      - name: Check if string starts with
+        if: startsWith('Hello world', 'He')
+        run: echo "The string starts with 'He'."
+
+      - name: Check if string ends with
+        if: endsWith('Hello world', 'ld')
+        run: echo "The string ends with 'ld'."
+
+      - name: Format and echo string
+        run: echo ${{ format('Hello {0} {1} {2}', 'Mona', 'the', 'Octocat') }}
+
+      - name: Join issue labels
+        if: github.event_name == 'issues'
+        run: "echo 'Issue labels: ${{ join(github.event.issue.labels.*.name, ", ") }}'"
+
+      - name: Convert job context to JSON
+        run: "echo 'Job context in JSON: ${{ toJSON(github.job) }}'"
+
+      - name: Parse JSON string
+        run: echo 'Parsed JSON: ${{ fromJSON("{\"hello\":\"world\"}").hello }}'
+
+      - name: Hash files
+        run: echo 'Hash of files: ${{ hashFiles("**/package-lock.json", "**/Gemfile.lock") }}'
+
+      - name: The job has succeeded
+        if: success()
+        run: echo "The job succeeded."
+
+      - name: The job has failed
+        if: failure()
+        run: echo "The job failed."