Add Getting started guide in Japanese

Author: seratch

docs/_config.yml

@@ -36,12 +36,11 @@ t:
     start: Getting started
     contribute: Contributing
   ja-jp:
-    basic: 基本的な概念
-    # TODO: translate this title
-    steps: Workflow steps
-    advanced: 応用コンセプト
+#    basic: 基本的な概念
+#    steps: ワークフローステップ
+#    advanced: 応用コンセプト
     start: Bolt 入門ガイド
-    contribute: 貢献
+#    contribute: 貢献
 
 # Metadata
 repo_name: bolt-python

docs/_includes/header.html

@@ -6,7 +6,7 @@
     {% if page.lang == "ja-jp" %}
       <a href="{{ site.url | append: site.baseurl }}/" class="header_btn language-switcher float_right">English</a>
     {% else %}
-      <!-- <a href="{{ site.url | append: site.baseurl }}/ja-jp" class="header_btn language-switcher float_right">日本語 (Japanese)</a> -->
+      <a href="{{ site.url | append: site.baseurl }}/ja-jp/tutorial/getting-started" class="header_btn language-switcher float_right">日本語 (Japanese)</a>
     {% endif %}
     </div>
 </div>