v2.0.1

• Restore improvements and fixes from v1.2.2 that were omitted from v2.0.0.
• Add an explicit error message when a radio material ( element) does not have a name attribute (#53, contributed by @hms0411rt)
• Fix Scene.render()'s colorbar not reflecting the cmap argument (#61, contributed by @14ndy15)
• Introduction tutorial: add information about Mitsuba variants (#62, contributed by @tiamilani)
• Introduction tutorial: fix typo (#64, contributed by @jeertmans)
• Diffraction tutorial: fix radio material update logic (#59, contributed by @Aburomoh)