add issue template

ISSUE_TEMPLATE.md

@@ -0,0 +1,25 @@
+<!--
+Hello! Thanks for contributing. 
+
+If you are reporting a bug, please:
+ - Make the issue title a succinct but specific description of the unexpected behavior. Bad: "Drawing line is broken". Good: "draw.changeMode('draw_line_string') throws an invalid options error"
+ - Include a link to a minimal demonstration of the bug. We recommend using https://jsbin.com
+ - Ensure you can reproduce the bug using the latest release.
+ - Check the console for relevant errors and warnings
+ - Only post to report a bug or request a feature. Direct all other questions to https://stackoverflow.com/questions/tagged/mapbox-gl-draw
+ 
+-->
+
+**mapbox-gl-js version**:
+**mapbox-gl-draw version**:
+
+### Steps to Trigger Behavior
+
+ 1.
+ 2.
+ 3.
+
+### Expected Behavior
+
+### Actual Behavior
+