Update infection

• Removed dev dependency on a dev-version of infection/infection

PHP 8.1 support

• BC Break: Added new keyword reserved in php 8.1 - readonly
• Add support for thecodingmachine/safe v2

PHP 8 support

• Added support for PHP 8.0
• BC Break: Dropped support of PHP 7.2
• BC Break: Added new keyword reserved in php 8 - match
• BC Break: Updated mixed keyword to reflect changes in php 8
• BC Break: Updated all keywords except namespace and __halt_compiler
  to reflect that they can be used as namespace parts since php 8.0
• BC Break: Added new method isReservedClassName to check for reserved words in
  class/trait/interface names. The method isReservedNamespaceName should
  be now used only for checking for reserved words in namespaces.
  These changes are necessary because php 8 changed the reserved words behavior for namespaces.
• Migrated CI to GitHub actions
• Added mutation testing
• Added phpstan static analysis

First release

1.0.0

Changed method names