Add initial code for mapping source plugin #5

src/Annotation/UiPatternsMappingSource.php

src/Plugin/UiPatternsMappingSourceBase.php

src/Plugin/UiPatternsMappingSourceInterface.php

src/Plugin/UiPatternsMappingSourceManager.php

src/UiPatternsManager.php

tests/target/composer.json

ui_patterns.api.php

ui_patterns.services.yml