Client-side HTML 5 validations

Add support for basic HTML 5 validations. I've think for now the only "safe" one with the least surprises and least amount of edge cases is marking HTML 5 fields as `required` on the client side if Superform detects a `validate presence: true` on a field. I'd like for the first commit or PR to start there, then each might add support for additional client-side validations per PR.