Add replyTo field support (#41)

Co-authored-by: Dawid Dziurla <dawidd0811@gmail.com>

action.yml

@@ -35,6 +35,9 @@ inputs:
   bcc:
     description: Blind carbon copy recipients (separated with comma)
     required: false
+  reply_to:
+    description: An email address that will appear on the Reply-To field
+    required: false
   ignore_cert:
     description: Allow unsigned/invalid certificates
     required: false