Add "documentation" category to PR template (#2195)

## Summary
1. Why:  to categorize documentation PRs
2. What: adds "documentation" category to the PR template

## Expected Behavior
- when users make documentation changes
- they should be able to specify documentation as a change category

## Actual Behavior
- no documentation category to specify

docs/pull_request_template.md

@@ -22,10 +22,11 @@
 4. <!-- use <detail> tag for large snippets -->
 
 ## Categorization
+- [ ] documentation
 - [ ] bugfix
 - [ ] new feature
 - [ ] refactor
-- [ ] CVE
+- [ ] security/CVE
 - [ ] other
 
 This PR resolves #<Replace-Me-With-The-Issue-Number-Addressed-By-This-PR> if any.