Flip 
by Farhan Kathawala @kathawala
Implement the type of `just-flip-object`. Examples:
```typescript
Flip<{ a: "x", b: "y", c: "z" }>; // {x: 'a', y: 'b', z: 'c'}
Flip<{ a: 1, b: 2, c: 3 }>; // {1: 'a', 2: 'b', 3: 'c'}
Flip<{ a: false, b: true }>; // {false: 'a', true: 'b'}
```
No need to support nested objects and values which cannot be object keys such as arrays
