Add initial list of maintainers

MAINTAINERS

+# The following is the list of current K3s maintainers
+# Github ID, Name, Email Address
+
+brandond, Brad Davidson, brad.davidson@rancher.com 
+briandown, Brian Downs, brian.downs@rancher.com 
+cjellick, Craig Jellick, craig@rancher.com 
+dweomer, Jacob Blain Christen, jacob@rancher.com
+erikwilson, Erik Wilson, erik@rancher.com
+galal-hussein, Hussein Galal, hussein@rancher.com 
+ibuildthecloud, Darren Shepherd, darren@rancher.com
+MonzElmasry, Menna Elmasry, menna.elmasry@rancher.com