Update PR template (#237)

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 -->