Add support for WebExtensions

[lonr]

Is your feature request related to a problem? Please describe.
No

Describe the feature you'd like
Add support for WebExtensions

VS Code Debugger for Firefox

[kyranjamie]

Seconding support for Web Extensions, especially with multiple JS contexts, an integrated debugger would be a huge productivity win.

[connor4312]

Seems like there are two things here:

1. We need to attach to browser-level frames and service workers, currently we filter and only attach to page types. This is easy to fix.
2. Sources in extensions get some random URL prefix like chrome-extension://gmocgbpbnimoncfocnbhifkbmcicoaef/service-worker.js. We don't have any way to map this in the debugger, and it seems like having a definite ID is not trivial.

I don't plan to support this in the foreseeable future, though if anyone has better solutions to #2, I'm happy to reconsider.

[victoralvelais]

@connor4312 #1794 shows that we can load an unpacked extension with runtimeArgs. Could we load an extension from our specified directory and then match the extension with the manifest keys? This wouldn't be as foolproof as setting a static ID but I think it would be easier for us to navigate at this time and cover most use cases.

[MoeBazziGIT]

Second this

[noorez]

Is there any possibility of reconsidering adding support for this?

Can something be borrowed if at all possible from: https://github.com/firefox-devtools/vscode-firefox-debug which does support debugging web extensions?