Update form guidelines

[mmenestr]

Want to update form guideline guidance around required fields and form validation.

Currently, in cases where every field in your form is required, we recommend writing "All fields are required" in grey at the top. Want to update this to be red, and also add guidance that this is optional -- if you think it will easily be missed in your case and having red asterisk in each field wouldn't feel too cluttered, feel free to just add the asterisk.

Also want to remove forced guidance of always disabling submit or next buttons until all fields are filled out correctly. This is because in some cases, having the ability to press the submit button is the only way to inform users of errors in a form. Instead, we want to just mention all possibilities for dealing with forms

• disabling until everything is filled out
• enabling to allow for error validation on submission
• field specific form validation