feat: expose the validation failure reasons for developers to check against

[JamesLMilner]

Description of Changes

This PR exposes all the internal validation failure reasons to make it easier for developers using Terra Draw to have branching logic depending on the failure reason, even if the wording of the error was to change in the future (for example due to a typo or clarification change).

import { ValidationReasons } from 'terra-draw';

const { ValidationReasonFeatureHasHoles } = ValidationReasons

console.log(ValidationReasonFeatureHasHoles)

Link to Issue

#380

PR Checklist

• The PR title follows the conventional commit standard
• There is a associated GitHub issue
• If I have added significant code changes, there are relevant tests
• If there are behaviour changes these are documented