Flybrains

* Add `JRC2018M` template brain, from the Bogovic and Saalfeld average template brains.

* Add `JRCVNC2018U` template nerve cord and surface, from the Bogovic
and Saalfeld average template brains. Thanks to istvantaisz (45,46)

* Add `JRCFIB2018F` Janelia electron microscopy hemibrain template brain; this
will help link EM connectomics and light level anatomical data (43)
* Add `JRC2018U` intersex template brain and surface, from the Bogovic
and Saalfeld average template brains. This intersex template brain from
may become the new registration standard. (41)
* Add `JRCVNC2018F` female template nerve cord and surface, from the Bogovic
and Saalfeld average template brains. Thanks to istvantaisz. (42)

* new github organisation: natverse/nat.flybrains
* other standard doc features for https://natverse.github.io packages
* fix DOI link for Dsim brain
* description for JRC2018F brain

* add citation

* Add `JRC2018F` female template brain and surface, the first of the Bogovic
and Saalfeld average template brains. The intersex template brain from
this series may become the new registration standard.