feat(Form): Add option for marking fields required

What does this MR do?

Updates contents/components/form.md to add an exception for forms where all fields are optional but 1-2:

Required information

We default to all information being required unless stated otherwise with "(optional)" added to the label of the corresponding input field.

However, if your form is entirely optional except for 1-2 fields, it might make sense to mark those as "(required)" instead

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