LibJS: Begin implementing console.dir

The intent of the spec is that the output of console.dir is interactable
within the console. Our Printer implementation currently just prints the
provided object as a string, and doesn't check the provided `options`
argument. But having console.dir defined prevents exceptions from being
thrown on real websites.

Userland/Libraries/LibJS/Runtime/CommonPropertyNames.h

@@ -151,6 +151,7 @@ namespace JS {
     P(deref)                                 \
     P(description)                           \
     P(difference)                            \
+    P(dir)                                   \
     P(direction)                             \
     P(disambiguation)                        \
     P(disposed)                              \