Make getContentType available for 3rd party usage (#7254)

* Refactored to make getContentType public for 3rd party use.

* Added missing "jpeg" extension

* Use getContentType() from mime namespace.

* Also add .jpeg extension

libraries/ESP8266WebServer/src/detail/mimetable.h

@@ -1,6 +1,7 @@
 #ifndef __MIMETABLE_H__
 #define __MIMETABLE_H__
 
+#include "WString.h"
 
 namespace mime
 {
@@ -16,6 +17,7 @@ enum type
   png,
   gif,
   jpg,
+  jpeg,
   ico,
   svg,
   ttf,
@@ -41,7 +43,8 @@ struct Entry
 
 
 extern const Entry mimeTable[maxType];
+
+String getContentType(const String& path);
 }
 
-
 #endif