addObserver issue fix: using context rather than activity in LocationServices

[vivekvardhanadepu]

fixes #67

[vatsal-gadhiya-searce]

@Richou Can we merge this please?

[anees17861]

@vivekvardhanadepu This doesn't address the actual issue properly. As suggested in the error, it needs to be called in main thread.
Instead of using reactContext try surrounding the location api with

new Handler(Looper.getMainLooper()).post(() -> {

})

This should make the call on main thread