AK: Allow specifying writability of a FixedMemoryStream

Author: https://github.com/kleinesfilmroellchen
Commit: bbeabe929b
Pull-request: https://github.com/SerenityOS/serenity/pull/21156
Reviewed-by: https://github.com/alimpfard
Reviewed-by: https://github.com/timschumi ✅

AK/MemoryStream.h

@@ -16,7 +16,7 @@ namespace AK {
 /// using a single read/write head.
 class FixedMemoryStream : public SeekableStream {
 public:
-    explicit FixedMemoryStream(Bytes bytes);
+    explicit FixedMemoryStream(Bytes bytes, bool writing_enabled = true);
     explicit FixedMemoryStream(ReadonlyBytes bytes);
 
     virtual bool is_eof() const override;