Expose wry navigation_handler via WindowBuilder closes #4080

[silvanshade]

What kind of change does this PR introduce?

• Bugfix
• Feature
• Docs
• New Binding issue #___
• Code style update
• Refactor
• Build-related changes
• Other, please describe:

Does this PR introduce a breaking change?

• Yes, and the changes were approved in issue #___
• No

Checklist

• When resolving issues, they are referenced in the PR's title (e.g fix: remove a typo, closes #___, #___)
• A change file is added if any packages will require a version bump due to this PR per the instructions in the readme.
• I have added a convincing reason for adding this feature, if necessary

Other information

Rationale

Currently, it is difficult to use tauri for certain situations, for example, those involving OAuth redirects. This has been noted in issues #3020, #5411, and elsewhere.

In some cases it is possible to find workarounds, such as by launching a local warp server and handling localhost redirects that way, but this is not always possible, particularly when the service in question uses deep linking and app-specific custom URI schemes.

A simple way to address this problem is to allow handling of URL navigation events with a callback configured for the webview. This is already possible now with wry using WebViewBuilder::with_navigation_handler. However, as far as I could tell, there was no way to access this functionality from wry directly through tauri prior to this PR.

This PR resolves that problem by allowing the user to set a navigation handler with tauri::WindowBuilder which then gets passed on to wry when the window is created via the runtime.

[silvanshade]

Fixes #5411.

[lucasfernog]

Nice PR, thanks!