dir option missing 'auto' support

[gvillo]

Hi! I found out that in manifest dir option is missing auto, source: https://docs.pwabuilder.com/#/builder/manifest?id=dir-string

    /**
     * @default `ltr`
     */
    dir: 'ltr' | 'rtl';

Auto will detect it based on text content

[userquin]

You can omit that entry in the PWA plugin options, the default value is not set here https://github.com/vite-pwa/vite-plugin-pwa/blob/main/src/options.ts#L105-L113 : manifest entry is declared as manifest: Partial<ManifestOptions> | false, we'll need to update the jsdocs.

Anyway, we need to add auto there and change the default value.