Translate getting-started.md to Japanese

[K-dash]

Related to #545

• まずはGetting Startedの日本語版Docを作成しました。

また、インストール可能な追加パッケージの説明として numpy が抜けていると思いましたので英語版Docの方にも追加しています。（認識誤りがありましたらご指摘ください）

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 91.04%. Comparing base (971b5ff) to head (8a6fae7). Report is 25 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #550 +/- ## ========================================== - Coverage 91.04% 91.04% -0.01% ========================================== Files 13 13 Lines 1931 1942 +11 Branches 431 437 +6 ========================================== + Hits 1758 1768 +10 Misses 117 117 - Partials 56 57 +1 ```

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