output installed version number after setup (#51)

* output installed version number after setup

* set output for the installed version

Author: rdaumann

action.yml

@@ -9,6 +9,9 @@ inputs:
   architecture:
     description: 'The target architecture (x86, x64) of the Python interpreter.'
     default: 'x64'
+outputs:
+  python-version:
+    description: "The installed python version. Useful when given a version range as input."
 runs:
   using: 'node12'
   main: 'dist/index.js'