feat: add Re:Earth favicon

[KaWaite]

Overview

What I've done

What I haven't done

How I tested

Screenshot

Which point I want you to review particularly

Memo

[netlify]

✅ Deploy Preview for reearth-web ready!

Name	Link
🔨 Latest commit	357e162
🔍 Latest deploy log	https://app.netlify.com/sites/reearth-web/deploys/6369f7f7d88a1a0009b68547
😎 Deploy Preview	https://deploy-preview-349--reearth-web.netlify.app/
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site settings.

[codecov]

Codecov Report

Merging #349 (357e162) into main (1efe8c3) will not change coverage.
The diff coverage is n/a.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #349   +/-   ##
=======================================
  Coverage   18.12%   18.12%           
=======================================
  Files         512      512           
  Lines       50945    50945           
  Branches      619      619           
=======================================
  Hits         9232     9232           
  Misses      41692    41692           
  Partials       21       21