Implement GitHub PR Issue Checker Workflow (#730)

**FIX** #719 

**Usage:**

1. When a pull request is created or edited, the workflow automatically
triggers.

2. The workflow checks for:
- A non-empty PR description.
- A valid issue reference format (`FIX #<issue-number>` or `FEAT, or DOC
#NEW`).
3. If either check fails, the PR will be marked as failing, and the
author will receive clear error messages in the PR comments.
4. If all checks pass, a confirmation message will indicate that the PR
is valid.

**_Note_**: Kindly add all the labels added to the issue, to this PR!

@UTSAVS26

.github/workflows/pr-checker.yaml

@@ -0,0 +1,91 @@
+name: PR Validation
+
+# Created by smog-root
+
+on:
+  pull_request:
+    types: [opened, edited]
+
+jobs:
+  validate-pr:
+    runs-on: ubuntu-latest
+
+    steps:
+    - name: Check out code
+      uses: actions/checkout@v3
+
+    - name: Set up Node.js
+      uses: actions/setup-node@v3
+      with:
+        node-version: '14'
+
+    - name: Validate PR Description
+      id: pr-check
+      run: |
+        # Fetch PR information
+        PR_DESCRIPTION=$(jq -r .pull_request.body < "$GITHUB_EVENT_PATH")
+        PR_TITLE=$(jq -r .pull_request.title < "$GITHUB_EVENT_PATH")
+
+        # Define file paths for the output variables
+        PR_VALID_FILE=$(mktemp)
+        ERROR_MESSAGE_FILE=$(mktemp)
+        SUCCESS_MESSAGE_FILE=$(mktemp)
+
+        # Default value for PR_VALID
+        PR_VALID="true"
+
+        # Check if PR description is empty
+        if [ -z "$PR_DESCRIPTION" ] || [ "$PR_DESCRIPTION" == "null" ]; then
+          echo "Empty PR description"
+          PR_VALID="false"
+          echo '❌ Error: PR description is empty!' > "$ERROR_MESSAGE_FILE"
+        fi
+
+        # Check for issue reference in the description
+        ISSUE_PATTERN="(Fixes|Close|Closes|Closed|Fix|Fixed|Resolve|Resolves) #[0-9]+"
+        if [[ ! "$PR_DESCRIPTION" =~ $ISSUE_PATTERN ]]; then
+          echo "Invalid or missing issue reference"
+          PR_VALID="false"
+          echo '❌ Error: PR must reference an issue with the format Fixes ,Close ,Closes ,Closed ,Fix ,Fixed ,Resolve ,Resolves #Issue_Number' > "$ERROR_MESSAGE_FILE"
+        fi
+
+        # If both checks pass
+        if [ "$PR_VALID" == "true" ]; then
+          echo '✅ Success: PR is valid!' > "$SUCCESS_MESSAGE_FILE"
+        fi
+
+        # Save the outputs to environment files
+        echo "PR_VALID=$PR_VALID" >> $GITHUB_ENV
+        echo "ERROR_MESSAGE=$(cat $ERROR_MESSAGE_FILE)" >> $GITHUB_ENV
+        echo "SUCCESS_MESSAGE=$(cat $SUCCESS_MESSAGE_FILE)" >> $GITHUB_ENV
+
+    - name: Post comment on PR
+      uses: actions/github-script@v6
+      with:
+        github-token: ${{ secrets.GITHUB_TOKEN }}
+        script: |
+          const prValid = process.env.PR_VALID;
+          const errorMessage = process.env.ERROR_MESSAGE;
+          const successMessage = process.env.SUCCESS_MESSAGE;
+          const prNumber = context.payload.pull_request.number;
+
+          if (prValid === 'false') {
+            github.rest.issues.createComment({
+              issue_number: prNumber,
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              body: errorMessage
+            });
+            core.setFailed(errorMessage);
+          } else {
+            github.rest.issues.createComment({
+              issue_number: prNumber,
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              body: successMessage
+            });
+          }
+
+    - name: Fail if validation failed
+      if: env.PR_VALID == 'false'
+      run: exit 1