AK: Expose the seekback limit of CircularBuffer

Author: https://github.com/timschumi
Commit: 52d9fc92f1
Pull-request: https://github.com/SerenityOS/serenity/pull/17884

AK/CircularBuffer.cpp

@@ -47,6 +47,11 @@ size_t CircularBuffer::capacity() const
     return m_buffer.size();
 }
 
+size_t CircularBuffer::seekback_limit() const
+{
+    return m_seekback_limit;
+}
+
 bool CircularBuffer::is_wrapping_around() const
 {
     return capacity() <= m_reading_head + m_used_space;