Update PR template (#219)

Author: samdark

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,7 +1,6 @@
 | Q             | A
 | ------------- | ---
-| Is bugfix?    | yes/no
-| New feature?  | yes/no
-| Breaks BC?    | yes/no
-| Tests pass?   | yes/no
-| Fixed issues  | comma-separated list of tickets # fixed by the PR, if any
+| Is bugfix?    | ✔️/❌
+| New feature?  | ✔️/❌
+| Breaks BC?    | ✔️/❌
+| Fixed issues  | <!-- comma-separated list of tickets # fixed by the PR, if any -->