Add template for Pull Requests (in-toto#155)

Signed-off-by: Prashant Rewar <[email protected]>

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,19 @@
+## What this PR does / why we need it
+
+Description
+
+## Which issue(s) this PR fixes (optional)
+
+(optional, using `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when the PR gets merged)*
+
+Fixes #
+
+## Acceptance Criteria Met
+
+- [ ] Docs changes if needed
+- [ ] Testing changes if needed
+- [ ] All workflow checks passing (automatically enforced)
+- [ ] All review conversations resolved (automatically enforced)
+- [ ] [DCO Sign-off](https://github.com/apps/dco)
+
+**Special notes for your reviewer**: