feat: add RTL language support (#531)

* feat: add RTL language support

- Add `SITE.dir` config option.
- Replace physical Tailwind classes with logical
property classes.

Resolves #439

* docs: add `dir` section in doc

src/config.ts

@@ -17,6 +17,7 @@ export const SITE = {
     url: "https://github.com/satnaing/astro-paper/edit/main/",
   },
   dynamicOgImage: true,
+  dir: "ltr", // "rtl" | "auto"
   lang: "en", // html lang code. Set this empty and default will be "en"
   timezone: "Asia/Bangkok", // Default global timezone (IANA format) https://en.wikipedia.org/wiki/List_of_tz_database_time_zones
 } as const;