PR to introduce the markerPosition prop to position the marker in regards to transform:translate(x,y).
The prop takes a string composed of the X axis value and Y axis value separated by a single white space
The prop can take following values for the X axis;

• left === 0
• center === -50%
• right === -100%

and the following for the Y axis;

• top === 0
• center === -50%
• bottom === -100%

For example

<GoogleMapReact>
<Marker markerPosition="left center"/>
</GoogleMapReact>