Update PULL_REQUEST_TEMPLATE.md

.github/PULL_REQUEST_TEMPLATE.md

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 # Summary
 
-This PR add the ability to do XYZ...
+e.g. This PR fixes ABC or adds the ability to do XYZ...
+
+**Related issues: #XYZ** (delete this line if there are no related issues)
 
 # Changes these areas
 
-- [ ] Config
 - [ ] Bugfixes
-- [ ] Command line interface
 - [ ] Feature behavior
-- [ ] Internal design
+- [ ] Command line interface
+- [ ] Configuration options
+- [ ] Internal architecture
 - [ ] Archived data layout on disk
 
 # Roadmap Goals
 
-This PR helps us move towards ____ roadmap goal, as outlined here: https://github.com/pirate/ArchiveBox#roadmap
+This PR helps us move towards xyz roadmap goal, as outlined here: https://github.com/pirate/ArchiveBox#roadmap
+(delete this section if it's just a bugfix / simple PR)