doc: documentation is now in the same repository as the code

Demo site will be generated in subfolder /demo

docs/config/i18n.md

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+# i18n
+
+Hugo has built-in support for multilingual sites. You can find more information about it in the [official documentation](https://gohugo.io/content-management/multilingual/).
+
+Translation files are placed in the `i18n` directory. The file name is the language code. For example, the `en.yaml` file is the translation file for English.
+
+In order to use a language, set `DefaultContentLanguage` to the language code in the configuration file. For example, if you want to use English, set `DefaultContentLanguage` to `en`.
+
+Currently, the theme supports the following languages:
+
+* `ar`: Arabic
+* `bn`: Bengali
+* `ca`: Catalan
+* `de`: German
+* `el`: Greek
+* `en`: English
+* `es`: Spanish
+* `fa`: Persian
+* `fr`: French
+* `hu`: Hungarian
+* `id`: Indonesian
+* `it`: Italian
+* `ja`: Japanese
+* `ko`: Korean
+* `nl`: Dutch
+* `pl`: Polish
+* `pt-br`: Portuguese
+* `ru`: Russian
+* `th`: Thai
+* `tr`: Turkish
+* `uk`: Ukrainian
+* `zh-cn`: Chinese (Simplified)
+* `zh-hk`: Chinese (Traditional) (Hong Kong)
+* `zh-tw`: Chinese (Traditional) (Taiwan)
+
+::: tip
+PRs for more language support are welcome 😉.
+:::