add issue template (new GitHub feature)

Author: gcanti

ISSUE_TEMPLATE.md

@@ -0,0 +1,27 @@
+### Version
+
+Tell us which versions you are using:
+
+- tcomb-form-native v0.?.?
+- react-native v0.?.?
+
+### Expected behaviour
+
+Tell us what should happen
+
+### Actual behaviour
+
+Tell us what happens instead
+
+### Steps to reproduce
+
+1.
+2.
+3.
+
+### Stack trace and console log
+
+Hint: it would help a lot if you enable the debugger ("Pause on exceptions" in the "Source" panel of Chrome dev tools) and spot the place where the error is thrown
+
+```
+```