The `code` directive highlights all sources as GDScript. Other languages are
highlighted incorrectly at the moment, even if `.. code:: [language]` is
specified.
It does, however, work with the `code-block` directive. The reason seems to be
that this directive is Sphinx specific.
There are a few places where no language is specified for a code block and
the default is incorrect.
There are a few places where pseudo code is treated as C++.