Add Enforce Specific Values With PropTypes as a react til

react/enforce-specific-values-with-proptypes.md

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+# Enforce Specific Values With PropTypes
+
+Being able to constrain our user interfaces to very specific values is
+valuable. This makes our interfaces easier to reason about and easier to
+test. PropTypes in general are one of the ways that we constrain our UIs. We
+can go even further than simple type constraints by limiting a prop to a
+specific set of values, an enum if you will.
+
+```javascript
+MyComponent.propTypes = {
+  flavors: PropTypes.oneOf(['Vanilla', 'Chocolate', 'Strawberry']),
+};
+```
+
+The docs say about `oneOf()`:
+
+> You can ensure that your prop is limited to specific values by treating it
+> as an enum.
+
+If we use `MyComponent` with a value such as `Pistachio`, we'll have a
+console warning to answer for.
+
+[source](https://reactjs.org/docs/typechecking-with-proptypes.html)