* Add preliminary notes for 1.8.4

Draft notes for 1.8.4
Signed-off-by: Miek Gieben <miek@miek.nl>

* Update notes/coredns-1.8.4.md
Co-authored-by: Chris O'Haver <cohaver@infoblox.com>

* Update notes/coredns-1.8.4.md
Co-authored-by: Chris O'Haver <cohaver@infoblox.com>

* Update notes/coredns-1.8.4.md
Co-authored-by: Chris O'Haver <cohaver@infoblox.com>
Co-authored-by: Chris O'Haver <cohaver@infoblox.com>