Enable Contracts on Hash instances, on keys themselves, on values themselves, and on elements at specific keys.

Supported contract types:

• of: combo of every_key and every_value as a Hash, more readable for types
• with: run on the value of specific keys (this is the default when using Hash[data])
• every: run on every [key, value] pair
• every_key: run on every key
• every_value: run on every value
• instance: run on the hash instance itself
• size: instance contract about size

Supported internal types of behaviour:

• every_key: run on every key
• every_key_value: run on every [key, value]
• every_value: run on every value
• keyword_args: run on the value of specific keys
• instance: run on the hash instance itself

Todo: add exemples.