Update ISSUE_TEMPLATE.md

Author: pitr-ch

.github/ISSUE_TEMPLATE.md

@@ -1,10 +1,11 @@
-<!-- Thank you for submitting an issue! -->
 
 
-
-<!-- Please fill following if applicable, delete otherwise: -->
-******
--   Operating system: linux / mac / win
--   `concurrent-ruby` version: x.y.z
--   `concurrent-ruby-ext` installed: yes / no
--   `concurrent-ruby-edge` used: yes / no
+<!-- Thank you for submitting an issue!. 
+     Please fill following if applicable, delete otherwise: -->
+```
+* Operating system:                linux / mac / win
+* Ruby implementation:             Ruby / JRuby / TruffleRuby / Rubinius
+* `concurrent-ruby` version:       x.y.z
+* `concurrent-ruby-ext` installed: yes / no
+* `concurrent-ruby-edge` used:     yes / no
+```