RS: 7.8.4 Feb/March maintenance release docs (#1220)

* DOC-4871 RS: Created release notes draft for RS 7.8.4 February maintenance release

* Added more bug fixes and highlights to the release notes draft

* DOC-4871 Added another resolved issue to the release notes draft

* DOC-4872 Added build number to release notes

* DOC-4872 Added checksums to release notes

Author: rrelledge