Merge pull request ipld/go-car#340 from ipld/ajnavarro-patch-1

This commit was moved from ipld/go-car@ca82390

ipld/car/cmd/car/README.md

@@ -16,11 +16,14 @@ USAGE:
 COMMANDS:
    create, c      Create a car file
    detach-index   Detach an index to a detached file
+   extract, x     Extract the contents of a car when the car encodes UnixFS data
    filter, f      Filter the CIDs in a car
    get-block, gb  Get a block out of a car
    get-dag, gd    Get a dag out of a car
    index, i       write out the car with an index
-   list, l        List the CIDs in a car
+   inspect        verifies a car and prints a basic report about its contents
+   list, l, ls    List the CIDs in a car
+   root           Get the root CID of a car
    verify, v      Verify a CAR is wellformed
    help, h        Shows a list of commands or help for one command
 ```