chore: Set default priority to P0 for all issues raised

Author: dishaprakash

.github/ISSUE_TEMPLATE/bug_report.md

@@ -1,6 +1,9 @@
 ---
 name: Bug report
 about: Create a report to help us improve
+title: ''
+labels: 'priority: p0'
+assignees: ''
 
 ---
 

.github/ISSUE_TEMPLATE/feature_request.md

@@ -1,6 +1,9 @@
 ---
 name: Feature request
 about: Suggest an idea for this library
+title: ''
+labels: 'priority: p0'
+assignees: ''
 
 ---
 

.github/ISSUE_TEMPLATE/support_request.md

@@ -1,6 +1,10 @@
 ---
 name: Support request
-about: If you have a support contract with Google, please create an issue in the Google Cloud Support console.
+about: If you have a support contract with Google, please create an issue in the Google
+  Cloud Support console.
+title: ''
+labels: 'priority: p0'
+assignees: ''
 
 ---