Sync return types for Blueprint::addColumn()

Merge pull request #4 from ajthinking/jbelien-patch-1

Update `Blueprint::addColumn()` return type

Add fromGeoJSON() and toGeoJSON()

Thanks to @jbelien 💫

Fix jsonSerialize deprecation warnings

v6.0.4

Update return types of jsonSerialize methods

Laravel 9 support

• Support Illuminate v9
• Devours bosnadev/database