Prefix/Suffix error state documentation/examples

[jamierthompson]

Add documentation for USDA-FSA/fsa-style#579

Completed and waiting in: https://github.com/USDA-FSA/fsa-design-system/tree/release/1.20.2

Just need to verify everything looks correct once fsa-style can be updated to 2.7.5 or greater in fsa-design-system

[jamierthompson]

Instructions updated

"Classes Added" section added to all error state examples

New prefix form field error example added (styling included in fsa-style release 2.7.5)

New suffix form field error example added (styling included in fsa-style release 2.7.5)

New textarea form field error example added