config: Add mediatypes section

config.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"mime"
 	"os"
 	"strings"
 	"text/template"
@@ -42,6 +43,10 @@ func (c *Config) Load(path string) error {
 			}
 		case "feeds":
 			c.Feeds[key] = value
+		case "mediatypes":
+			for _, field := range strings.Fields(value) {
+				mime.AddExtensionType(key, field)
+			}
 		}
 	})
 }