Firefox Debugger does not work

Issue Type: Performance Issue

When I installed the Debugger for Firefox 2.9.1 from Visual Studio Code, it appears in the list of the available Debugging environments, but when I start a debugging session it seems to stop without any error message.

Extension version: 2.9.1
VS Code version: Code 1.51.1 (e5a624b788d92b8d34d1392e4c4d9789406efe8f, 2020-11-10T23:34:32.027Z)
OS version: Windows_NT x64 10.0.18363

System Info

|Item|Value|
|---|---|
|CPUs|Intel(R) Core(TM) i7-4770K CPU @ 3.50GHz (8 x 3498)|
|GPU Status|2d_canvas: enabled
flash_3d: enabled
flash_stage3d: enabled
flash_stage3d_baseline: enabled
gpu_compositing: enabled
multiple_raster_threads: enabled_on
oop_rasterization: disabled_off
opengl: enabled_on
protected_video_decode: unavailable_off
rasterization: enabled
skia_renderer: disabled_off_ok
video_decode: enabled
vulkan: disabled_off
webgl: enabled
webgl2: enabled|
|Load (avg)|undefined|
|Memory (System)|15.94GB (12.02GB free)|
|Process Argv|--crash-reporter-id b0c0959a-561b-46aa-a447-df43237a4b8f|
|Screen Reader|no|
|VM|50%|

Process Info

```
CPU % Mem MB PID Process
0 72 7644 code main
0 12 3044 crashpad-handler
0 66 4228 shared-process
0 25 7664 utility
0 151 7936 window (SiteServer.js - REDMEN_UK_WEBSITE - Visual Studio Code)
0 11 8772 watcherService
0 6 8824 console-window-host (Windows internal process)
0 67 10504 C:\WINDOWS\System32\WindowsPowerShell\v1.0\powershell.exe
0 62 10804 extensionHost
0 66 7536 electron_node tsserver.js
0 89 9192 electron_node tsserver.js
0 41 2220 electron_node typingsInstaller.js typesMap.js
0 6 11272 console-window-host (Windows internal process)
1 57 12612 window (Issue Reporter)
0 68 12764 gpu-process
```

Workspace Info

```
| Window (SiteServer.js - REDMEN_UK_WEBSITE - Visual Studio Code)
| Folder (REDMEN_UK_WEBSITE): 28 files
| File types: jpg(11) png(7) html(2) js(2) css(2)
| Conf files:;
```

Reproduce a debugging session using Firefox Debugger 2.9.1, VS Code 1.51.1, and Windows 10, then inspect the extension's available diagnostics for why the session stops silently. Done means identifying a reproducible cause and making the session start successfully, or documenting actionable failure evidence if the problem cannot be reproduced.

Written by the indexing model from the issue text.