You can quickly switch between LTR & RTL mode using the Toggle button. You can make default RTL mode by updating below changes in the src/layouts/Layouts.astro file.
x-data="{ direction: 'rtl', mode: 'dark' }" dir="rtl"
At line no: 23 you just update the direction: 'rtl' or 'ltr' and
At line no: 26 set dir="rtl" so it will be set by default.