docs(README.md): fix a typo
docs(README.md): fix a typo

* Original commit: 6ea2f48c0ff743e1318526ed1f19fa06ac089f0d
* Original author: @andela-rekemezie 
* Closes #357 
jossi87/react-google-maps,jossi87/react-google-maps,tomchentw/react-google-maps,RishabhJain96/react-google-maps,RishabhJain96/react-google-maps