Update fieldset guidance to clarify use of required

[SmartMouthWords]

Received user questions about labelling fieldsets as required.

Update guidance to include points that summarize the following:
We do not recommend adding the ("required") marker in a fieldset legend when indicating that all form fields within the group are required. When the fieldset legend acts as a label for a form field however, like it would when used with a checkbox or a radio button group, then it is appropriate to add the required marker in that scenario. Otherwise, the recommendation is to place the required marker on each individual form field label.

To do:

• draft point(s) to add to coding guidance
• validate
• translate
• bilingual review

[SmartMouthWords]