Code-server for jupyterhub

[mvdebolskiy]

Hi, I've been tryint to get code-server working with jupyterhub/singleuser-base-notebook image, However, syntax highlighting (vscode-textmate/vscode-onigurama) is not working (unlike with spark image). Tried different code-server versions (installed from install.sh and through npm) and options for the ServerApp (in jupyter_server_config.py). Judging by debug output, webWorkerExtensionHostIframe is failing as well as onig.wasm is not creating.