Issue #3346969: Allow users to set which plugins to use or not use

config/install/structured_data_generator.settings.yml

config/schema/structured_data_generator.schema.yml

src/Form/StructuredDataGeneratorSettingsForm.php

src/StructuredDataGeneratorAttachments.php

structured_data_generator.install

structured_data_generator.links.menu.yml

structured_data_generator.permissions.yml

structured_data_generator.routing.yml