add reminder `init.lua` is optional

README.md

@@ -55,6 +55,8 @@ A few tutorials have already been written to help people write plugins in Lua. S
 
 Neovim supports loading an `init.lua` file for configuration instead of the usual `init.vim`.
 
+Note: `init.lua` is of course *completely* optional. Support for `init.vim` is not going away and is still a valid option for configuration. Do keep in mind that some features are not 100% exposed to Lua yet.
+
 See also:
 - `:help config`
 

doc/nvim-lua-guide.txt

@@ -92,6 +92,11 @@ init.lua~
 Neovim supports loading an `init.lua` file for configuration instead of
 the usual `init.vim`.
 
+Note: `init.lua` is of course *completely* optional. Support
+for `init.vim` is not going away and is still a valid option for
+configuration. Do keep in mind that some features are not 100% exposed
+to Lua yet.
+
 See also:
 - |config|