add validation meta

[nicknisi]

Type: feature

The following has been addressed in the PR:

• There is a related issue (Add validation support for text-input widgets#664)
• All code has been formatted with prettier as per the readme code style guidelines
• Unit or Functional tests are included in the PR

Description:

This PR adds a new meta that specifically returns information from the browser's form validation API. This can be used to target HTML form elements, such as <input type="email">, and will return an object containing information about whether the element passes validation and whether it contains a message.

Invalid Example

Given the following:

render() {
    const value = 'test';
    const validity = this.meta(InputValidity).get('input', value);
    render (
        <input type="email" key="input" value={value}/>
    )
}

This meta will return the following:

{
    valid: false,
    message: "Please include an '@' in the email address. 'test' is missing an '@'."
}

Valid Example

Given the following:

render() {
    const value = 'test@example.com';
    const validity = this.meta(InputValidity).get('input', value);
    render (
        <input type="email" key="input" value={value}/>
    )
}

This meta will return the following:

{
    valid: true,
    message: ""
}

[tomdye]

👍