atob and btoa are not defined

- VS Code Version: 1.36.1
- OS Version: Windows 10 Pro 10.0.17134
- Code Runner Version: 0.9.11

**Describe the bug**
atob and btoa are not defined.

**To Reproduce**
Steps to reproduce the behavior:

1. Create a small JS snippet `btoa("test")`
2. Execute the snippet

**Actual behavior**
ReferenceError: atob is not defined

**Expected behavior**
I'd expect it to base64 encode/decode the text.