patterns to generate test data for vstorage clients

[dckc]

As an app author, I'd like to test my code against all possible values that I might get from vstorage.
If vstorage writers publish patterns, we should be able to generate fast-check Arbitrary instances to approximate "all possible values".

IOU pointers to

• issue on generating typescript types from patterns
• existing work on testing with fast-check-ava for AmountMath etc.
• using patterns to validate vstorage data in a inter bid list PR