docs: update bug report template for v3 (#867)

- Remove outdated v0.1.x CodeSandbox link
- Add note about using v3.x with Pane component API
- Add StackBlitz as alternative reproduction option
- Add Environment section for version info

Fixes #865

Author: tomkp

.github/ISSUE_TEMPLATE/bug_report.md

@@ -18,7 +18,9 @@ Steps to reproduce the behavior:
 
 or
 
-Post a link to a [CodeSandbox](https://codesandbox.io/). You can start by forking [this one](https://codesandbox.io/s/mz305w3yoy).
+Post a link to a reproduction using [StackBlitz](https://stackblitz.com/) or [CodeSandbox](https://codesandbox.io/).
+
+> **Note:** Make sure you're using react-split-pane v3.x with the new `<Pane>` component API. See the [README](https://github.com/tomkp/react-split-pane#readme) for usage examples.
 
 #### Expected behavior
 
@@ -28,6 +30,13 @@ A clear and concise description of what you expected to happen.
 
 If applicable, add screenshots to help explain your problem.
 
+#### Environment
+
+- react-split-pane version:
+- React version:
+- Browser:
+- OS:
+
 #### Additional context
 
 Add any other context about the problem here.