Is your feature request related to a problem? Please describe:

There's currently an issue with the authentication flow where in some cases upon calling the Callback URL (default myapp.firebaseapp.com/__/auth/handler provided by Firebase) the external browser will show this error:
"Unable to process request due to missing initial state. This may happen if browser sessionStorage is inaccessible or accidentally cleared."

There's a GitHub issue open for this: firebase/firebase-js-sdk#4256

From my own testing and troubleshooting I've concluded that in my experience this only happens with mobile Firefox. However, if we go to Firefox advanced settings and toggle "Open Links in App" to on, then the authentication proceeds as normal by redirecting back to the Capacitor app. Other browsers tested such as Chrome, Brave and Samsung Internet all work normally.

This leads me to believe that if force the authentication to open in a WebView, then we normalize the experience for all users, regardless of what their default web browser is set to.

Describe the solution you'd like:

If possible, force (or as configurable option) the authentication flow to go through @capacitor/browser instead of an external browser.

Additional context:

I'm unsure if the solution belongs to this plugin, but I thought this was a good place to start. Any advice appreciated!