fix(doc): Add note about mime-type for POST /binaries API

Fixes spark-jobserver#792

Author: noorul

README.md

@@ -765,7 +765,7 @@ Flow diagrams are checked in in the doc/ subdirectory.  .diagram files are for w
     POST /binaries/<appName>    - upload a new binary file
     DELETE /binaries/<appName>  - delete defined binary
 
-When POSTing new binaries, the content-type header must be set to one of the types supported by the subclasses of the `BinaryType` trait. e.g. "application/java-archive" or application/python-archive"
+When POSTing new binaries, the content-type header must be set to one of the types supported by the subclasses of the `BinaryType` trait. e.g. "application/java-archive" or application/python-archive". If you are using curl command, then you must pass "-H 'Content-Type: application/python-archive'" or "-H 'Content-Type: application/java-archive'".
 
 ### Jars (deprecated)