Build: Copy LibJS/Tests into /home/anon/js-tests

The test runner currently depends on the bash port being installed.
If you have it, you can run the LibJS test suite inside Serenity
by simply entering /home/anon/js-tests and doing ./run-tests :^)

Kernel/build-root-filesystem.sh

@@ -95,6 +95,7 @@ printf "installing users... "
 mkdir -p mnt/home/anon
 mkdir -p mnt/home/nona
 cp ../ReadMe.md mnt/home/anon/
+cp -r ../Libraries/LibJS/Tests mnt/home/anon/LibJS-Tests
 chmod 700 mnt/home/anon
 chmod 700 mnt/home/nona
 chown -R 100:100 mnt/home/anon