Header button text scales incorrectly when Large Text is enabled on iOS

[wongk]

Precondition: iOS Settings > Accessibility > Display & Text Size > Larger Text: enabled larger text and increase the font size a noticeable amount.

Add a simple header button as shown in the repo README. The button text scales at the same rate as other text in the app, which is not how the system scales header text. Header text scales more slowly. Additionally, there is a bug in either Expo or React Navigation that causes other header text to not be scaled at all. So we end up with a button with fully scaled text next to other header text that isn't scaled at all. Here's a screenshot:

Here's a screenshot of Apple Health, which demonstrates how the header text should be handled:

I recommend that, since Expo/React Navigation are not scaling text at all, that this library do the same. It's as simple as passing allowFontScaling={false} in defaultRenderVisibleButton.