Adds deprecation notice
Adds deprecation notice

Which is taken from [here](https://github.com/perl6/roast/blob/master/docs/announce/6.d.md)

MasterDuke17/doc,MasterDuke17/doc,tbrowder/doc,perl6/doc,tbrowder/doc,perl6/doc,perl6/doc,perl6/doc,perl6/doc,MasterDuke17/doc,tbrowder/doc,MasterDuke17/doc,tbrowder/doc