[RN] Input.Text masking/password support #91

Ref: microsoft#4673

Requirements
Need to evaluate the implementation using secure strings

Security concerns about submitting the data is plain-text Call out in documentation that this is not cryptographically secure

If the underlying control supports the 'Show Password' button, it should be on; otherwise, no requirement for this

When style is set to password, the multiline property should be ignored.

Validation should run on the password

Examples
{
"type": "Input.Text",
"id": "secretThing",
"style": "password"
}