Added option to toggle reader mode for links on iOS

[hjiangsu]

Pull Request Description

This PR adds a way to toggle reader mode on iOS when tapping on an external link. This only works when openInExternalBrowser is false as it relies on flutter_custom_tabs parameter.

Issue Being Fixed

Issue Number: #760

Screenshots / Recordings

10de1507-1c78-461c-974b-033af7f3f3f5.mp4

Checklist

• Did you update CHANGELOG.md?
• Did you use localized strings where applicable?
• Did you add semanticLabels where applicable for accessibility?

[micahmo]

LGTM!

BTW, I had an idea to bring back the in-app browser you developed with three options (in-app browser, custom tabs, external browser). I thought some people might like the more app-native experience better, and it might allow us to integrate some third-party reader mode on Android (if such a thing exists).

[hjiangsu]

BTW, I had an idea to bring back the in-app browser you developed with three options (in-app browser, custom tabs, external browser)

Hmm, I wonder if there are any users who prefer the in-app browser more than the custom tabs. I haven't heard anything myself but if this is the case, then we can definitely do this!

[micahmo]

I wonder if there are any users who prefer the in-app browser more than the custom tabs.

Not that they prefer it, per se, but that they want features which would required it. One example would be #729. We can't handle swipe gestures on the custom tabs, but we probably could in app. Another would be, for example, a comment button that jumps straight from a web page to the post comments (like Relay has).

[hjiangsu]

Ahh I see, that makes sense!