support "stringy booleans", for some types of data only

[karenetheridge]

For some payloads, e.g. query parameters that are exploded into an object from a string, a value might convey a boolean value but was represented as a string. Provide an option to allow strings that match true or false to be validated as a boolean value:

When this configuration is enabled (default false),

data "false" and "true" will validate successfully against

• "type": "boolean"
• "type": ["boolean", ..]
• "const": true or "const": false
• "enum": [true, false]

[karenetheridge]

meh? YAGNI? why can't we just say "enum":["true","false"] instead, because the range of values for booleans is so limited?