Support no launch.json debugging

Hi VS Code PM here 👋

We would love if firefox debug would support debugging without a `launch.json`. Thus allowing users to debug in a no folder vscode.
Easiest to do this is to have a dynamic `resolveDebugConfiguartion` that will provide a launch configuration on the fly. [Example](https://github.com/microsoft/vscode-mock-debug/blob/main/src/activateMockDebug.ts#L161)

Apart from that consider contributing to the Editor title area menu, such that a Play button would appear in the Editor Title area (picture below). Example how to do this https://github.com/microsoft/vscode-mock-debug/blob/main/package.json#L80

I think both of these are super important and would really love that we improve this experience 💯
Let me know if I can help somehow. I am also open to a quick 30 min meeting where we can discuss about the new cool VS Code debug features that firefox debug could potentially adopt.

Comienza localizando los puntos de entrada para la activación y configuración del depurador en este repositorio y, después, compáralos con el ejemplo referenciado activateMockDebug.ts para resolveDebugConfiguration. Revisa el ejemplo referenciado de package.json para el menú del área del título del Editor. El trabajo estará terminado cuando se admita la depuración sin launch.json y se muestre la acción Play solicitada en el área del título del editor.

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