Allow plus signs in 'to' and 'from' entities.

Author: tsalo

templateflow/conf/config.json

@@ -52,11 +52,11 @@
         },
         {
             "name": "from",
-            "pattern": "(?:^|_)from-([a-zA-Z0-9]+).*xfm"
+            "pattern": "(?:^|_)from-([a-zA-Z0-9+]+).*xfm"
         },
         {
             "name": "to",
-            "pattern": "(?:^|_)to-([a-zA-Z0-9]+).*xfm"
+            "pattern": "(?:^|_)to-([a-zA-Z0-9+]+).*xfm"
         },
         {
             "name": "mode",