feat: add crystal filetype (#3762)

Add crystal filetype

lua/lvim/config/settings.lua

@@ -69,6 +69,7 @@ M.load_default_options = function()
     extension = {
       tex = "tex",
       zir = "zir",
+      cr = "crystal",
     },
     pattern = {
       ["[jt]sconfig.*.json"] = "jsonc",