Recommend GrapheneOS over LineageOS on Pixel phones

[secretmango]

On Pixels it makes little sense to install LineageOS.

I would at least add a button to get to GrapheneOSses install page. They have two methods, I dont have a native chrome browser, so I used the script and it worked great.

https://grapheneos.org/install/cli

This could be packaged in the tool, it uses basic ADB Fastboot stuff

[tsterbak]

There might still be a lot of reasons for people to install LineageOS or something else on Pixel devices.

Nevertheless, GrapheneOS is great and I would generally recommend it. But since they have nice installation methods, I see little reason to add it in this Installer.

This could be done with #221 (without handle installation process)