Add a release checklist as a RST document.

Author: ntoll

RELEASE_TODO.rst

@@ -0,0 +1,9 @@
+Checklist for Releases
+======================
+
+* Update the version number in the editor.html file.
+* Update the CHANGES.rst file with English description of changes made.
+* If required, update the firmware.hex file to the correct version of the "vanilla" MicroPython runtime used in this release.
+* Create a tagged release using GitHub.
+* Inform those who maintain the versioning manifest. Currently this is @jaustin at the micro:bit foundation.
+