chore: add ISSUE_TEMPLATE.md (#2141)

.github/ISSUE_TEMPLATE.md

@@ -0,0 +1,16 @@
+<!--
+Thank you for reporting an issue.
+
+Please fill in as much of the template below as you're able.
+
+C3 version: The c3 version number which is available from `c3.version`.
+Browser: The browser version.
+OS: The operating system.
+
+If possible, please provide codepen or jsfiddle example that demonstrates the problem, keeping it as
+simple and free of external dependencies as you are able.
+-->
+
+* **C3 version**:
+* **Browser**:
+* **OS**: