LibWeb: Introduce the File interface from the FileAPI spec

Author: https://github.com/kennethmyhra
Commit: 890514a057
Pull-request: https://github.com/SerenityOS/serenity/pull/14694
Reviewed-by: https://github.com/linusg
Reviewed-by: https://github.com/trflynn89

Userland/Libraries/LibWeb/FileAPI/Blob.h

@@ -54,6 +54,9 @@ public:
 
     ReadonlyBytes bytes() const { return m_byte_buffer.bytes(); }
 
+protected:
+    Blob(ByteBuffer byte_buffer);
+
 private:
     Blob() = default;