Please add documentation on validation for manager forms

[yiqi0110-glitch]

As per @tidyui request in the closed issue, any comments on this would be greatly appreciated. This link is what I am currently basing the project off. Thanks!

[Filip]

Hi!

The manager is based on Bootstrap so the Bootstrap documentation can be really helpful.
As for form validation, we can uses the Bootstrap way of doing it.

But the different here is instead of using the needs-validation class on the form element, we just look for the validate class on a form element.

Maybe it could be a good ide to change/add so that the class needs-validation also can be used, as shown in the examples.

BR
Filip