* A few different types of validation
* Rename
* Fix test
* Updating validation framework
* Update lockfile
* Ensure validators can be None
* Reworking the API a little
* Convert Input.Changed to dataclass
* Add utility for getting failures as strings
* Update an example in Validator docstring
* Remove some redundant `pass`es
* Renaming variables
* Validating Input on submit, attaching result to Submitted event
* Testing various validation features
* Update snapshots and deps
* Styling unfocused -invalid Input differently
* Add snapshot test around input validation and associated styles
* Validation docs
* Tidying validation docs in Input widget reference
* Fix mypy issues
* Remove __bool__ from Failure, make validator field required
* Code review changes
* Improving error messages in Validators
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