feat: add getExtensions method to extend zoid component instance

[ravishekhar]

• We have a use case where its necessary to add support for additional methods on the Zoid component instance.
• To support this use case getExtensions callback is being added to create method.
• Zoid would call this method to add the additional properties returned by this callback on the component instances.
• This method will accept the parent props as an argument so that the extended methods could interact with props passed during initialization.
• The implementation will ensure that getExtensions cannot override any of the existing methods in Zoid like render, clone etc.

Sample usage

const MyComponent = zoid.create({
    tag: "custom-buttons",
    getExtensions: (parent) => {
     // methods defined in parent props, like `onCancel` will be available in 
     // props returned by parent.getProps();
      return {
        hasReturned: () => true,
        resume: () => {
          console.log("Resuming ....");
        },
      };
    }
});

const component = MyComponent({ 
     onCancel: function() { ... }
})

Now the component instance will contain the additional methods along with standard methods.
e.g.

component.hasReturned(); // will return true
component.resume(); // will log Resuming .... on console.