Add guideline regarding "optional" and "required" in form components

[sandra-post]

As per discussion, add guideline to documentation how to mark optional and required fields in a form.

Add to documentation of:

• [x] Text input
• [x] Text area
• [x] Select
• [x] Checkbox
• [x] Radio
• [x] Switch

[sandra-post]

Created documentation component , added instance to components mentioned. See Figma comment.