RNFetchBlob.fs.readFile default settings doesnt function

[hasancanozkan]

RN: 0.47.1
fetch-blob: 0.10.8
I just realized that RNFetchBlob.fs.readFile default setting doesnt work, i have to specify 'utf8' in the Promise. This could also be related the issue #450 , because I was getting the same error if i dont specify utf8. I hope you fix this

[lll000111]

I'll add a patch to my upcoming pull request for 0.10.9.