docs: switch language based on current path

docs/src/_data/sites/en.yml

@@ -85,6 +85,7 @@ footer:
     description: Selecting a language will take you to the ESLint website in that language.
     change_language: Change Language
     language: Language
+    latest: Latest
   copyright: >
     &copy; OpenJS Foundation and ESLint contributors, <a href="https://www.openjsf.org">www.openjsf.org</a>
   links:

docs/src/_data/sites/zh-hans.yml

@@ -84,6 +84,7 @@ footer:
     description: 切换到你所选择语言版本对应的 ESLint 网站。
     change_language: 更改语言
     language: 语言
+    latest: 最新
   copyright: >
     &copy; OpenJS Foundation and ESLint contributors, <a href="https://www.openjsf.org">www.openjsf.org</a>
   links:

docs/src/_includes/components/language-switcher.html

@@ -14,9 +14,14 @@
         <select name="language selector" id="language-select" aria-describedby="language-infobox"
             class="c-custom-select switcher__select">
             {% for key, other_site in sites %}
-            <option value="{{ other_site.language.code }}" data-url="https://{{ other_site.hostname }}" {% if
-                site.language.code==other_site.language.code %} selected {% endif %}>
+            <option
+                value="{{ other_site.language.code }}"
+                data-url="https://{{ other_site.hostname }}/docs/latest{{ page.url | prettyURL }}"
+                {% if site.language.code==other_site.language.code %}selected{% endif %}
+            >
                 {{ other_site.language.flag }} {{ other_site.language.name }}
+                {% if site.language.code!=other_site.language.code %}({{ other_site.footer.language_switcher.latest }})
+                {% elif GIT_BRANCH=="latest" %}({{ other_site.footer.language_switcher.latest }}){% endif %}
             </option>
             {% endfor %}
         </select>