Remote Debugging Cursor not visible in vscode.

> Version 2.2.0 of the debug adapter supports remote development. Please try it out and tell me if it works for you.

@hbenl I can set and hit a breakpoint in vscode in a JS file, this shows in the vscode debugging toolbar, as well as the firefox debugger, while I can Step Over or Step In using either the vscode debugging toolbar or the firefox debugger -- I can only see where what line the cursor is on in the firefox debugger -- **I can't see what line the cursor is on in the vscode JS file.**

The vscode instance is running in a .devcontainer, while the firefox browser (`firefox -start-debugger-server -dev-tools`) is running on the host (my laptop).

```
{
// https://github.com/firefox-devtools/vscode-firefox-debug
// Before attaching, start Firefox from a host terminal using the following:
// firefox -start-debugger-server -dev-tools
"name": "Firefox: attach localhost:5000",
"type": "firefox",
"request": "attach",
"url": "http://localhost:5000",
"webRoot": "${workspaceFolder}/application"
}
```

_Originally posted by @jonfen in https://github.com/firefox-devtools/vscode-firefox-debug/issues/104#issuecomment-548568174_