compatible with RN > 0.49

[alzalabany]

RN > 0.49 requires to implement requiresMainQueueSetup.
this fix and suppress that yellow box warning

Module RNFetchBlob requires main queue setup since it overrides `init` but doesn't implement `requiresMainQueueSetup`. In a future release React Native will default to initializing all native modules on a background thread unless explicitly opted-out of.

[Traviskn]

We are currently expecting pull requests with bugfixes to be applied to the 0.10.9 branch.

We merged another pull request #10 on that branch that implemented requiresMainQueueSetup, but returns YES instead of NO. Can you give any details on why we should not require main queue setup?

[wedneyyuri]

requiresMainQueueSetup must return true when it requires being set up on the main queue. That can be for various reasons, like accessing UIKit API or doing some other, thread-aware actions.
https://twitter.com/grabbou/status/941309557082640384

If a module overrides constantsToExport and doesn't implement requiresMainQueueSetup, then react-native must assume that it must be called on the main thread, because it may need to access UIKit.
https://github.com/facebook/react-native/blob/b9e7006cc6dc2b0801ea0c776ba00cdea2204151/React/Base/RCTModuleData.mm#L41

[Traviskn]

@wedneyyuri Thanks for the additional info!