fix input

Author: m4rc1e

action.yml

@@ -20,7 +20,7 @@ inputs:
     description: 'Width of diff images. Default is 1280px'
     required: false
     default: 1280
-  template-dir:
+  template_dir:
     description: 'Directory to custom html test pages. If no directory is provided, use gftools/templates'
     required: false
     default: 'none'