pull_request_template_update: Added Documentation PR Type (#158)

.github/PULL_REQUEST_TEMPLATE.md

@@ -15,6 +15,7 @@ try to push all related PRs at the same time.
 - [ ] New feature (change that adds new functionality)
 - [ ] New test (change that adds new test program and/or testbench)
 - [ ] Breaking change (has dependencies in other repositories/testbenches)
+- [ ] Documentation (change that adds or modifies documentation)
 
 ## PR Checklist
 - [ ] I have followed the code style guidelines
@@ -24,4 +25,4 @@ try to push all related PRs at the same time.
 - [ ] I have signed off all commits from this PR
 - [ ] I have updated the documentation (wiki pages, ReadMe files, Copyright etc)
 - [ ] I have not introduced new Warnings/Errors on compilation/elaboration/simulation
-- [ ] I have set the verbosity level to none for the test program
+- [ ] I have set the verbosity level to none for the test program