docs: added documentation for toast component changes (#7141)

* docs: added documentation for toast component changes

* added redirect from use-toast docs to upgrade guide

* remove unused file

* content linting fixes

* update UI package version

* updated ui preset

* fix upgrade guides main page

www/apps/ui/src/examples/toaster-error.tsx

@@ -1,17 +1,13 @@
-import { Button, Toaster, useToast } from "@medusajs/ui"
+import { Button, Toaster, toast } from "@medusajs/ui"
 
 export default function ToasterError() {
-  const { toast } = useToast()
-
   return (
     <>
       <Toaster />
       <Button
         onClick={() =>
-          toast({
-            title: "Error",
+          toast.error("Error", {
             description: "The quick brown fox jumps over the lazy dog.",
-            variant: "error",
             duration: 5000,
           })
         }