feat: Fix pull request template by adding spaces to checkboxes (#103)

The pull request template currently renders incorrectly due to a lack of
spacing within the square brackets. The spaces looked optional in GitHub
documentation, and the issue was not obvious until merged and used.

Author: ADubhlaoich

.github/pull_request_template.md

@@ -21,15 +21,15 @@ Closes #ISSUE
 
 Before merging a pull request, run through this checklist and mark each as complete.
 
-- [] I have read the [contributing guidelines](/CONTRIBUTING.md)
-- [] I have signed the [F5 Contributor License Agreement (CLA)](https://github.com/f5/.github/blob/main/CLA/cla-markdown.md)
-- [] I have ensured that documentation content adheres to [the style guide](/templates/style-guide.md)
-- [] If the change involves potentially sensitive changes, I have assessed the possible impact
-- [] If applicable, I have added tests that prove my fix is effective or that my feature works
-- [] If applicable, I have checked that any relevant tests pass after adding my changes
-- [] I have updated any relevant documentation ([`README.md`](/README.md) and [`CHANGELOG.md`](/CHANGELOG.md))
-- [] I have rebased my branch onto main
-- [] I will ensure my PR is targeting the main branch and pulling from my branch from my own fork
+- [ ] I have read the [contributing guidelines](/CONTRIBUTING.md)
+- [ ] I have signed the [F5 Contributor License Agreement (CLA)](https://github.com/f5/.github/blob/main/CLA/cla-markdown.md)
+- [ ] I have ensured that documentation content adheres to [the style guide](/templates/style-guide.md)
+- [ ] If the change involves potentially sensitive changes, I have assessed the possible impact
+- [ ] If applicable, I have added tests that prove my fix is effective or that my feature works
+- [ ] If applicable, I have checked that any relevant tests pass after adding my changes
+- [ ] I have updated any relevant documentation ([`README.md`](/README.md) and [`CHANGELOG.md`](/CHANGELOG.md))
+- [ ] I have rebased my branch onto main
+- [ ] I will ensure my PR is targeting the main branch and pulling from my branch from my own fork
 
 Potentially sensitive changes include anything involving code, personally identify information (PII), live URLs or significant amounts of new or revised documentation.