load Map From Asset
This function is responsible for loading the Map content from Json file that is located the assets folder of the application. it takes the context of the application and the name of the JSON file as parameters. then it reads the JSON file and returns it as a string.
Return
the JSON file as a string or null if the file is not found
Parameters
context
the context of the application
file Name
the name of the JSON file
Throws
if the file is not found