create issue template

.github/issue_template.md

@@ -0,0 +1,18 @@
+**OS:**
+<!-- Specify platform should be sufficient (i.e. WIN/LINUX/OSX/..) -->
+
+
+**Godot version:**
+<!-- Specify commit hash if non-official. -->
+
+
+**Blender version:**
+<!-- Specify commit hash if non-official. -->
+
+
+**Issue description:**
+<!-- What happened, and what was expected. -->
+
+
+**Minimal reproduction project:**
+<!-- Recommended as it greatly speeds up debugging. Drag and drop a zip archive to upload it. -->