docs: add missing pointers to Files API calls

Author: daviddias

README.md

@@ -165,7 +165,11 @@ $ ipfs config --json API.HTTPHeaders.Access-Control-Allow-Methods "[\"PUT\", \"P
   - [`ipfs.files.addReadableStream([options])`](https://github.com/ipfs/interface-ipfs-core/tree/master/SPEC/FILES.md#addreadablestream)
   - [`ipfs.files.addPullStream([options])`](https://github.com/ipfs/interface-ipfs-core/tree/master/SPEC/FILES.md#addpullstream)
   - [`ipfs.files.cat(multihash, [callback])`](https://github.com/ipfs/interface-ipfs-core/tree/master/SPEC/FILES.md#cat). Alias to `ipfs.cat`.
+  - [`ipfs.files.catReadableStream([options])`](https://github.com/ipfs/interface-ipfs-core/tree/master/SPEC/FILES.md#catreadablestream)
+  - [`ipfs.files.catPullStream([options])`](https://github.com/ipfs/interface-ipfs-core/tree/master/SPEC/FILES.md#catpullstream)  
   - [`ipfs.files.get(hash, [callback])`](https://github.com/ipfs/interface-ipfs-core/tree/master/SPEC/FILES.md#get). Alias to `ipfs.get`.
+  - [`ipfs.files.getReadableStream([options])`](https://github.com/ipfs/interface-ipfs-core/tree/master/SPEC/FILES.md#getreadablestream)
+  - [`ipfs.files.getPullStream([options])`](https://github.com/ipfs/interface-ipfs-core/tree/master/SPEC/FILES.md#getpullstream)  
   - `ipfs.ls`
   - MFS (mutable file system) specific:
     - `ipfs.files.cp`