Documentation update to fix build error on Android.

[hugoh59]

Need to update the docs to reflect the new folder name for the module:

• project(':react-native-fetch-blob').projectDir = new File(rootProject.projectDir, '../node_modules/react-native-fetch-blob/android')

• project(':react-native-fetch-blob').projectDir = new File(rootProject.projectDir, '../node_modules/rn-fetch-blob/android')

[Traviskn]

We would love to have a PR for doc updates 😃