fix typo (#16)

Author: raulb

README.md

@@ -19,7 +19,7 @@ go get github.com/conduitio/ecdysis
 ```
 
 To create a new command, define a struct that implements `ecdysis.Command` and
-any other `ecdysis.CommandWih*` interfaces you need. The recommended pattern is
+any other `ecdysis.CommandWith*` interfaces you need. The recommended pattern is
 to list the interfaces that the command implements in a `var` block.
 
 ```go
@@ -214,4 +214,4 @@ A full list of supported tags:
 - `hidden`: Whether the flag is hidden (i.e. not shown in help)
 
 For a more example on how to use persistent flags in subcommands, see the
-[example](./example).
+[example](./example).