README: fix a typo

Signed-off-by: Antoine Tenart <antoine.tenart@ack.tf>

README.md

@@ -2,4 +2,4 @@
 
 Serve is a stupid simple program to share files and directories over http from
 the command line. It is written in Go and can also be used to stream videos or
-big files, where Pyhton's SimpleHTTPServer can't.
+big files, where Python's SimpleHTTPServer can't.