Update Release notes

Author: Speierers

docs/release_notes.rst

@@ -11,6 +11,36 @@ Incoming release
 
 - TBA
 
+Mitsuba 2.1.0
+-------------
+
+*May 19, 2020*
+
+- Switch to OptiX 7 for GPU ray tracing backend (`#88 <https://github.com/mitsuba-renderer/mitsuba2/pull/88>`_)
+- Mesh memory layout redesign (`#88 <https://github.com/mitsuba-renderer/mitsuba2/pull/88>`_)
+- Custom shape support for OptiX raytracing backend (`#135 <https://github.com/mitsuba-renderer/mitsuba2/pull/135>`_)
+- ``xml.dict_to_xml()`` for writing XML scene file from Python (`#131 <https://github.com/mitsuba-renderer/mitsuba2/pull/131>`_)
+
+Mitsuba 2.0.1
+-------------
+
+*May 18, 2020*
+
+- ``xml.load_dict()`` for Mitsuba scene/object construction in Python (`#122 <https://github.com/mitsuba-renderer/mitsuba2/pull/122>`_)
+- Scene traversal mechanism enhancement (`#108 <https://github.com/mitsuba-renderer/mitsuba2/pull/108>`_)
+- Support premultiplied alpha correctly (`#104 <https://github.com/mitsuba-renderer/mitsuba2/pull/104>`_)
+- Spot light plugin (`#100 <https://github.com/mitsuba-renderer/mitsuba2/pull/100>`_)
+- Add Blender mesh constructor (`40db7be <https://github.com/mitsuba-renderer/mitsuba2/commit/40db7be01215>`_)
+- Irradiancemeter sensor plugin (`b19985b <https://github.com/mitsuba-renderer/mitsuba2/commit/b19985b28568>`_)
+- Radiancemeter sensor plugin (`#83 <https://github.com/mitsuba-renderer/mitsuba2/pull/83>`_)
+- Distant emitter plugin (`#60 <https://github.com/mitsuba-renderer/mitsuba2/pull/60>`_)
+- Custom shape support for Embree raytracing backend (`2c1b63f <https://github.com/mitsuba-renderer/mitsuba2/commit/2c1b63f9d1de>`_)
+- Add ability to specify Python default variant (`4472b55 <https://github.com/mitsuba-renderer/mitsuba2/commit/4472b55d080f>`_)
+- Add pytest -m "not slow" option (`4597466 <https://github.com/mitsuba-renderer/mitsuba2/commit/4597466d8ca7>`_)
+- Moment integrator and Z-tests (`74b2bf6 <https://github.com/mitsuba-renderer/mitsuba2/commit/74b2bf658c7f>`_)
+- Spatially-varying `alpha` for roughconductor and roughdielectric (`cac8741 <https://github.com/mitsuba-renderer/mitsuba2/commit/cac8741de935>`_)
+- Various bug fixes and other improvements
+
 Mitsuba 2.0.0
 -------------