docs: add a note to the default values to the readme

Author: daviddias

README.md

@@ -120,7 +120,7 @@ The last published version of the package become [available for download](htt
 
 The `jsipfs` CLI, available when `js-ipfs` is installed globably, follows(should, it is a WIP) the same interface defined by `go-ipfs`, you can always use the `help` command for help menus.
 
-```
+```sh
 # Install js-ipfs globally
 > npm install ipfs --global
 > jsipfs --help
@@ -134,6 +134,12 @@ Commands:
 # ...
 ```
 
+`js-ipfs` uses some different default config values, so that they don't clash directly with a go-ipfs node running in the same machine. These are:
+
+- default repo location: `~/.jsipfs` (can be changed with env variable `IPFS_PATH`)
+- default swarm port: `4002`
+- default API port: `5002`
+
 ### HTTP-API
 
 The HTTP-API exposed by the js-ipfs daemon follows the [`http-api-spec`](https://github.com/ipfs/http-api-spec). You can use any of the IPFS HTTP-API client libraries with it, such as: [js-ipfs-api](https://github.com/ipfs/js-ipfs-api).