docs: Update README.md (#728)

Author: flipflopsimsommer

README.md

@@ -279,7 +279,7 @@ $ ipfs config --json API.HTTPHeaders.Access-Control-Allow-Methods "[\"PUT\", \"P
   - [`ipfs.repo.version([callback])`](https://github.com/ipfs/interface-ipfs-core/tree/master/SPEC/REPO.md#version)
   
 - [key](https://github.com/ipfs/interface-ipfs-core/blob/master/SPEC/KEY.md)
-  - [`ipfs.key.gen(name, [options, callback])`](https://github.com/ipfs/interface-ipfs-core/blob/master/SPEC/KEY.md#javascript---ipfskeygenname-options-callback)
+  - [`ipfs.key.gen(name, options, [callback])`](https://github.com/ipfs/interface-ipfs-core/blob/master/SPEC/KEY.md#javascript---ipfskeygenname-options-callback)
   - [`ipfs.key.list([options, callback])`](https://github.com/ipfs/interface-ipfs-core/blob/master/SPEC/KEY.md#javascript---ipfskeylistcallback)
   - [`ipfs.key.rm(name, [callback])`](https://github.com/ipfs/interface-ipfs-core/blob/master/SPEC/KEY.md#javascript---ipfskeyrmname-callback)
   - [`ipfs.key.rename(oldName, newName, [callback])`](https://github.com/ipfs/interface-ipfs-core/blob/master/SPEC/KEY.md#javascript---ipfskeyrenameoldname-newname-callback)