Import all this stuff into a single repo called Serenity.

AK/StringBuilder.cpp

@@ -0,0 +1,25 @@
+#include "StringBuilder.h"
+
+namespace AK {
+
+void StringBuilder::append(String&& str)
+{
+    m_strings.append(std::move(str));
+}
+
+void StringBuilder::append(char ch)
+{
+    m_strings.append(StringImpl::create(&ch, 1));
+}
+
+String StringBuilder::build()
+{
+    auto strings = std::move(m_strings);
+    if (strings.isEmpty())
+        return String::empty();
+
+    return String();
+}
+
+}
+