Fixed readme, changed return values

• Removed wrong requirement of PHP 8 in the readme
• Changed return values of some of the methods to the flag value instead of the class itself

PHP 7.4 +

• More type-safety
• some tests
• an additional "toggle" helper method

Full Changelog: v1.0.1...v2.0.0

Minor update

Fixed setter to allow method-chaining

v1.0: Update composer.json

Added version number to mark it as first stable release