use stricter regex

Author: mtrezza

src/ParseFile.js

@@ -43,7 +43,7 @@ export type FileSource =
     };
 
 const base64Regex = new RegExp(
-  '([0-9a-zA-Z+/]{4})*(([0-9a-zA-Z+/]{2}==)|([0-9a-zA-Z+/]{3}=)|([0-9a-zA-Z+/]{4}))',
+  '([0-9a-zA-Z+/]{4})*(([0-9a-zA-Z+/][AQgw]==)|([0-9a-zA-Z+/]{2}[AEIMQUYcgkosw048]=)|([0-9a-zA-Z+/]{4}))',
   'i'
 );