Added read only / disabled flag to some components

[ViRuSTriNiTy]

see pkp/pkp-lib#5705

• FieldAutosuggest, FieldText, FieldTextarea, added read only flag
• FieldSelect, added disabled flag

[NateWr]

Thanks @ViRuSTriNiTy! I think we need to make this a consistent prop across all of our fields, rather than adding it to just a few, and then document the prop as well. This entails the following:

1. Add isReadonly to the props for FieldBase, so that every component that extends that one will be able to use the property.
2. When defining the property, provide a default like this:

isReadonly: {
  type: Boolean,
  default() {
    return false;
  }
}

3. Make sure that every field makes use of the property where appropriate, except for case like FieldHTML which doesn't input a value anyway.

[NateWr]

Also, I'd like to see us standardize on isDisabled and isReadonly. They can have the same CSS styles applied to them, but apply the different disabled and readonly HTML attributes. If I recall correctly, the readonly attribute allows someone to interact with a field (like select text) but not change it, whereas the disabled attribute prevents someone from selecting text at all.

[asmecher]

(One important distinction between disabled and readonly is the user's ability to scroll through long content to read it. That's not possible with a disabled field. So in cases like a metadata form that can't currently be edited but is still viewable/readable, readonly is a less frustrating user experience than disabled.)