docs: update to next 15 + eslint 9 (#9839)

* update next

* updated react

* update eslint

* finish updating eslint

* fix content lint errors

* fix docs test

* fix vale action

* fix installation errors

www/packages/docs-ui/src/components/MainNav/DesktopMenu/index.tsx

@@ -23,7 +23,7 @@ import { MenuItem } from "types"
 export const MainNavDesktopMenu = () => {
   const [isOpen, setIsOpen] = useState(false)
   const { setDesktopSidebarOpen, isSidebarShown } = useSidebar()
-  const ref = useRef(null)
+  const ref = useRef<HTMLDivElement>(null)
 
   useClickOutside({
     elmRef: ref,

www/packages/docs-ui/src/components/MainNav/MobileMenu/index.tsx

@@ -5,6 +5,7 @@ import { Button } from "../../Button"
 import { ArrowUturnLeft, BarsThree, XMark } from "@medusajs/icons"
 import clsx from "clsx"
 import { MenuItem } from "types"
+// @ts-expect-error can't install the types package because it doesn't support React v19
 import { CSSTransition, SwitchTransition } from "react-transition-group"
 import { MainNavMobileMainMenu } from "./Main"
 import { MainNavMobileSubMenu } from "./SubMenu"