breaking: deprecate zenflesh and allow zenbones bg=dark

This is an interim change to prepare removing zenflesh. Please make use
of zenbones and set bg=dark to get the zenflesh colors.

lua/zenflesh/init.lua

@@ -1,4 +1,9 @@
 local generator = require "zenbones.specs"
 local p = require "zenflesh.palette"
 
+vim.notify(
+	"zenflesh is deprecated. Please use zenbones and set background=dark.",
+	vim.log.levels.WARN,
+	{ title = "zenbones" }
+)
 return generator.generate(p, "dark", generator.get_global_config "zenflesh")