v0.19.0

• Added. Bounded constructive generation for prefixItems/contains
  (including minContains/maxContains), dependentRequired,
  dependentSchemas, and unevaluatedProperties/unevaluatedItems (#157).
• Added. Conditional schemas (if/then/else) are generated
  constructively, including boolean and nested branches. Each candidate is
  checked by openapi-contract's SchemaCheck; unreachable branches are
  omitted and a conditional with no finite value fails closed (#157).
• Fixed. A member under patternProperties is now generated against the
  schema of the name it actually lands under. The value was compiled once for
  the whole map, so every name received the schema of whichever name was drawn
  first — an object whose ^a member carried a boolean and whose z$ member
  carried a string, which the contract rejects (#157).
• Changed. Requires rasuvaeff/openapi-contract ^0.16 (in place of
  ^0.15) for the schema keywords added in 0.16: prefixItems, contains
  with minContains/maxContains, dependentRequired, dependentSchemas,
  unevaluatedProperties/unevaluatedItems (#157).