Merge pull request #76 from wimski/feature/attachment-factory-extendi…

…bility

Extract attachment instance creation in factory to improve extendibility

Fixed ensure printable check for null input

Interpolator could not handle null values for a mixed type

Made json variants data handling more robust

Allow variant steps without array wrap in steps()

Fixed phpstan issues up to level 7

Changelog updated

PHP 8.0+ release

Added test for order of auto-orient & resize variant steps

Changelog updated

Fixed too lenient testbench support for Laravel 6.0 max version