Announce that migration to GitHub has been completed

Author: uenoB

docs/en/index.md

@@ -15,6 +15,3 @@ fun f x = ignore (puts (#b x))
 val _ = f {a = "Hi", b = "Hello"}
 val _ = f {b = "World", c = "SML#"}
 ```
-
-Currently, we are working on migration to GitHub.
-[Visit old SML# website in Tohoku University](https://www.pllab.riec.tohoku.ac.jp/smlsharp/)

docs/en/news/_posts/2021-04-07-github-migration-completed.md

@@ -0,0 +1,21 @@
+---
+title: "GitHub migration completed"
+translated: true
+---
+
+We are pleased to announce that we have completed migration to GitHub!
+
+From now on, we will develop SML# by using public repositories on GitHub and
+offer information from this website (GitHub Pages).
+We will use GitHub Issues, Pull requests, and Discussions as the primary
+channel for communiction between developers and users.
+See the [development] page for details.
+The [previous website] and mail address we used are still available for a while.
+
+During the migration process, we made "force push" over and over again.
+If you forked or cloned a repository in the [smlsharp organization] before
+6 Apr 2021, please fork or clone again.
+
+[smlsharp organization]: https://github.com/smlsharp
+[previous website]: https://www.pllab.riec.tohoku.ac.jp/smlsharp/
+[development]: ../../development/index.md

docs/ja/index.md

@@ -11,5 +11,3 @@ fun f x = ignore (puts (#b x))
 val _ = f {a = "Hi", b = "Hello"}
 val _ = f {b = "World", c = "SML#"}
 ```
-
-現在GitHubへの移行作業中です。[東北大学の旧SML# Webサイトを見る](https://www.pllab.riec.tohoku.ac.jp/smlsharp/ja/)

docs/ja/news/_posts/2021-04-07-github-migration-completed.md

@@ -0,0 +1,14 @@
+---
+title: "GitHubへの移行が完了しました"
+translated: true
+---
+
+SML#プロジェクトのGitHubへの移行が完了しました。
+
+今後はGitHub上の公開リポジトリでSML#の開発を行い、このWebサイト（GitHub Pages）で情報を発信していきます。また、GitHub Issues、Pull requests、Discussionsが、SML#開発チームと連絡を取るチャネルとなります。詳しくは[開発]のページをご覧ください。[これまでのWebサイト]やメールアドレスも暫くの間は有効です。
+
+移行作業中は色々と試行錯誤を重ね、幾度となくforce pushを行いました。2021年4月6日以前に[smlsharp organization]のリポジトリをforkまたはcloneした方がいらっしゃいましたら、再度forkまたはcloneをお願いいたします。
+
+[smlsharp organization]: https://github.com/smlsharp
+[これまでのWebサイト]: https://www.pllab.riec.tohoku.ac.jp/smlsharp/ja/
+[開発]: ../../development/index.md