iOS: Add formSheetPreferredContentSize prop to allow for custom sized formSheet modals

[ShaneMckenna23]

PR Checklist

• The PR title follows our guidelines: https://github.com/proyecto26/react-native-inappbrowser/blob/main/CONTRIBUTING.md#pull-request-process.
• There is an issue for the bug/feature this PR is for. To avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it.
• All existing tests are passing
• Tests for the changes are included

What is the current behavior?

Unable to define the size of formSheet modals on iPad

What is the new behavior?

Added new prop to allow for custom sized formSheet modals on iPad.

Implements #330.

Migration steps:

• No migration steos needed, new prop is optional.

Screenshots

width-500-height-800.mov

width-500-height-600.mov

[jdnichollsc]

Hey mate, this is amazing!

One question, what happen with the modal if the device is rotated with the browser open? 🤔

Thanks for your contribution! <3

[jdnichollsc]

Thanks for your amazing contribution dude! <3