Feature: Archiving

[ianrumac]

Changes in this pull request

• Adds web archives feature, allowing Superwall to save paywalls to the users disk and keep them as long as they are valid, enabling Superwall to load them from the disk
• Adds shouldArchive option which works in tandem with shouldPreload, enabling you to either archive and preload the paywalls, just archive or just preload

Checklist

• All unit tests pass.
• All UI tests pass.
• Demo project builds and runs.
• I added/updated tests or detailed why my change isn't tested.
• I added an entry to the CHANGELOG.md for any breaking changes, enhancements, or bug fixes.
• I have run ktlint in the main directory and fixed any issues.
• I have updated the SDK documentation as well as the online docs.
• I have reviewed the contributing guide