Added support for Neovim package manager lazy.nvim (#293)

* Added support for lazy.nvim

From https://github.com/folke/lazy.nvim
Authored-by: Jacob Lane Ledbetter <jledbetter460@gmail.com>

src/steps/upgrade.vim

@@ -38,6 +38,11 @@ if exists(":CocUpdateSync")
     CocUpdateSync
 endif
 
+if exists(":Lazy")
+    echo "Lazy"
+    Lazy update
+endif
+
 " TODO: Should this be after `PackerSync`?
 " Not sure how to sequence this after Packer without doing something weird
 " with that `PackerComplete` autocommand.