Form Validation for WIP Limits
We need to have form validation and messages when a user inputs a non-numerical input, details found [here](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/22552#note_276193257)
I think we need to validate against the following:
- Number
- Negative Number
- ~~Max wip limit? (Would this be valuable?)~~
- Decimals
issue