[Feature] Other Funding Description validation

[thetif]

Based on design task #3439

Mockups or link to Figma https://www.figma.com/file/6eVvo7JjvXiovGTR4BoVgK/CMS-eAPD-2021?node-id=5604%3A38747

Acceptance criteria

Error message only displays under Other Funding Description if error checking is on.

Given	When	Then
error checking is on and other funding description is blank	other funding amount is blank	error message does not display
error checking is on and other funding description is blank	other funding amount is $0	error message does not display
error checking is on and other funding description is blank	other funding amount is > $0	error message displays
error checking is off and other funding description has any value	other funding amount has any value	error message does not display

This task is done when…

• [ ] all acceptance criteria are met