feat: add desktop support to flutter example

[Corbie-42]

Add build targets Linux, macOS and Windows.

This was done by executing:

flutter create --platforms=windows,macos,linux --project-name ory_network_flutter flutter-ory-network

and adjusting the clientId of the GoogleSignIn in main.dart, so that it is (currently) disabled on desktop.

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.

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[Corbie-42]

Okay, I see that you

1. expect the conventional commits to have an unconventional list of commit titles as body
2. expect the copyright year to be updated on the first PR on master
3. require the CLA to be singed. I don't want my email address to be linked to this account, so I won't sign the CLA. Feel free to reproduce the steps or take over this PR.

[vinckr]

Hello @Corbie-42 Thanks for your contribution! I will see to bring the repo in order soon. Should be a week or two until I find time to take a closer look at this.

The commits check just failed because it expects a conventional commit PR title, fixed it.

As for the CLA there is unfortunately no way around signing it as we might want to use your contribution in our documentation etc.