Make rn-fetch-blob a peer dependency #33
Description
In the same way that react-native is not a direct dependency, rn-fetch-blob should be a peer dependency.
Users may already have a direct dependency on this in their project - ideally this wouldn't be duplicated. It also allows users to use other (compatible) versions of rn-fetch-blob which may include bug fixes.
It can be added as a dev dependency for the tests to run, if necessary. The minimum compatible react-native version should also be specified as a peer dependency.