feat: add LargeHeaderSubtitleComponent

[aharwood9]

Description

Closes #24. Adds a LargeHeaderSubtitleComponent to all the containers so that a component can be added to the ListHeaderComponent/ScrollView.

Motivation and Context

I would like to add additional components to the ListHeader that don't get impact the header animation. For example, several lines of text.

How Has This Been Tested?

This has been tested in both the Simple ScrollView and the FlatList in the example. I have added the subtitle to the ScrollView for future testing.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• I have followed the guidelines in the README.md file.
• I have updated the documentation as necessary.
• My changes generate no new warnings.

Screenshots

Additional Notes (Optional)

Please include any additional information or context that may be helpful for the reviewer.

[aharwood9]

@e-younan - This should be ready for review. I have updated the simple example to use the new subtitle header as the subtitle is relatively simple and don't want to impact the design of the twitter one etc.

I have updated the docs to include the new prop as well. I am not sure how you want to visualise this - I am not sure if this is required.

[e-younan]

LGTM, great work!

[e-younan]

Feel free to check out the latest version on npm!