#91: Adding pattern definition as class.

src/Definition/PatternDefinition.php

src/Plugin/DataType/Pattern.php

src/Plugin/DataType/PatternDefinition.php

src/Plugin/Deriver/AbstractDeriver.php

src/TypedData/PatternDataDefinition.php

src/UiPatterns.php

tests/src/Kernel/TypedData/PatternDataDefinitionTest.php

tests/src/fixtures/validation.yml