fix(TS): add focusin/focusout typings (#183)

**What**:
Add typings for the new focusin/focusout events

**Why**:

Enables the new API to be used from TypeScript

**Checklist**:

- [ ] Documentation N/A
- [ ] Tests N/A
- [x] Ready to be merged <!-- In your opinion, is this ready to be merged as soon as it's reviewed? -->
- [x] Added myself to contributors table <!-- this is optional, see the contributing guidelines for instructions -->

Author: RoystonS

typings/events.d.ts

@@ -10,6 +10,8 @@ export type EventType =
   | 'keyUp'
   | 'focus'
   | 'blur'
+  | 'focusIn'
+  | 'focusOut'
   | 'change'
   | 'input'
   | 'invalid'