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:;
```

Firefox Debugger 2.9.1、VS Code 1.51.1、Windows 10 を使用してデバッグセッションを再現し、その後、セッションが何も表示せずに停止する理由を調べるために、拡張機能で利用可能な診断情報を確認します。再現可能な原因を特定してセッションを正常に開始できるようにするか、問題を再現できない場合に実行可能な失敗の証拠を文書化できれば完了です。

索引モデルが issue の本文から書いたものです。