🌐 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.

templates/macros/add_comments.html

@@ -86,7 +86,7 @@
 {% if automatic_loading %}
     <script src="{{ get_url(path='js/' ~ comment_system ~ '.min.js', trailing_slash=false) | safe }}" async></script>
 {% else %}
-    <button id="load-comments" class="load-comments-button" data-script-src="{{ get_url(path='js/' ~ comment_system ~ '.min.js', trailing_slash=false) | safe }}">{{ macros_translate::translate(key="load_comments", default="Load comments") }}</button>
+    <button id="load-comments" class="load-comments-button" data-script-src="{{ get_url(path='js/' ~ comment_system ~ '.min.js', trailing_slash=false) | safe }}">{{ macros_translate::translate(key="load_comments", default="Load comments", language_strings=language_strings) }}</button>
     <script src="{{ get_url(path='js/loadComments.min.js', trailing_slash=false) | safe }}" async></script>
 {% endif %}