Update PR template

Add a checklist item that the new entry has a reason for being
considered garbage.

Signed-off-by: Joe Block <[email protected]>

Author: unixorn

.github/PULL_REQUEST_TEMPLATE.md

@@ -21,5 +21,6 @@
 <!--- Go over all the following points, and put an `x` in all the boxes that apply. [x] -->
 <!--- If you're unsure about any of these, don't hesitate to ask. I'm happy to help! -->
 
+- [ ] I included a description and/or links in the new entry's garbage column describing _why_ it is garbage.
 - [ ] All new and existing tests pass.
 - [ ] I have confirmed that the link(s) in my PR are valid.