🌐 feat(i18n): overhaul translation system & add languages (#145)

Revamp the existing translation system, simplifying
management and adding several new languages. The new system reads from
TOML files in the `/i18n` directory and improves template structures.
It also enhances customisation options and robustness by providing
fallbacks and modularity.

- Implement a new, streamlined translation macro.
- Load translations from `/i18n` TOML files.
- Remove redundant configuration requirements.
- Refactor templates to align with new i18n system.
- Add support for Hindi, Japanese, Russian, Portuguese, Chinese,
  Italian, German, Ukranian, Korean, and French languages.
- Credit Thomas Weitzel (@thomasweitzel) for inspiration.

README.md

@@ -14,7 +14,8 @@ tabi has a perfect score on Google's Lighthouse audit:
 
 ## Features
 
-- [X] Multi-language support.
+- [X] [Comprehensive multi-language support](https://welpo.github.io/tabi/blog/faq-languages/#how-does-tabi-handle-multilingual-support). Add as many languages as you wish.
+- [X] [Set any language as default](https://welpo.github.io/tabi/blog/faq-languages/#how-do-i-set-a-default-language-for-my-site). Set your base site to Chinese, Spanish, French, Hindi… or any [other supported language](/i18n). The theme's interface will be translated accordingly.
 - [X] Dark and light themes. Defaults to the OS setting, with a switcher in the navigation bar.
 - [X] Support for [comments using giscus, utterances, Hyvor Talk, or Isso](https://welpo.github.io/tabi/blog/comments/).
 - [X] Perfect Lighthouse score (Performance, Accessibility, Best Practices and SEO).
@@ -106,13 +107,13 @@ header = {title = "Hello! I'm tabi~", img = "img/main.webp" }
 
 The content outside the front matter will be rendered between the header title and the posts listing. In the screenshot above, it's the text that reads "tabi is a fast, lightweight, and modern Zola theme…".
 
-6. If you want a multilingual site, you will need to set up each language. In `config.toml`:
+6. If you want a multilingual site, you will need to set up each language. In `config.toml`, set the title and taxonomies for each language, like:
 
-- set the translations for a few strings;
-- set the title and taxonomies for each language;
-- add the `language_name.{code}` in `[extra]`. This is the text shown in the language switcher.
-
-See [these lines in the provided `config.toml`](https://github.com/welpo/tabi/blob/main/config.toml#L22-L134) for an example.
+```toml
+[languages.es]
+title = "~/tabi"
+taxonomies = [{name = "tags", feed = true}]
+```
 
 You will need an `_index.{language_code}.md` per language for each section (e.g. /blog or /projects) that you want to enable in that language.
 
@@ -120,6 +121,8 @@ The same is true for individual posts, which should have the exact same name as
 
 This configuration allows the language switcher to take the user to the translation of the current URL. If a translation doesn't exist, the 404 page will be displayed, with an explanation in each language set in the config.
 
+To learn more about multilingual support, see the [Frequently Asked Questions](https://welpo.github.io/tabi/blog/faq-languages/).
+
 ## Inspiration
 
 This theme was inspired by:
@@ -130,7 +133,9 @@ This theme was inspired by:
 
 ## Contributing
 
-Please do! Take a look at the [Contributing Guidelines](/CONTRIBUTING.md) to learn more.
+Please do! We appreciate bug reports, improvements to translations or documentation (however minor), feature requests…
+
+Take a look at the [Contributing Guidelines](/CONTRIBUTING.md) to learn more.
 
 ## License