🌐 Add Japanese translation for tutorial/first-steps.md

[tokusumi]

This PR translates the tutorial/first-steps.md to Japanese.
Please review tutorial/first-steps.md.

Issue #1571 generates a new directory to support Japanese.
I will fix dependency after #1571 is merged.

[codecov]

Codecov Report

Merging #1658 into master will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##            master     #1658   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          239       239           
  Lines         7079      7079           
=========================================
  Hits          7079      7079           

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[ryuckel]

I checked Japanese translation. I have no proposal of change about this document. Thank you so much!

[github-actions]

📝 Docs preview for commit 2250eb7 at: https://5f37d173c3f45f090fe0dc44--fastapi.netlify.app

[SwftAlpc]

It's almost perfect!
I was wondering about some of the details, so if you would like to correct them, please do so.

[SwftAlpc]

I thought it would be better to abstract.

[SwftAlpc]

I think it's so much better!

[github-actions]

📝 Docs preview for commit 3007ed1 at: https://5f381722c3f45f1723e0d931--fastapi.netlify.app

[github-actions]

📝 Docs preview for commit 4c0a572 at: https://5f4a708046d5ad4319178f04--fastapi.netlify.app

[tokusumi]

Hi, @tiangolo
This PR has been approved by two reviewers (github actions to label approved PR didn't work, though).
Would you like to require something more for this to be merged?

[tiangolo]

Excellent! Thank you for doing it @tokusumi ! 🙇 🍰

And thanks @ryuckel and @SwftAlpc for the reviews 👏 👏 🤓