Consolidate Logos and update README header (#14136)

* Consolidate Logos and update README header

- Remove unused `logo-lg.png`, `logo-sm.png` and `logo-192.png`.
- Consolidate `favicon.svg` and `logo.svg` to just `logo.svg`.
- Remove Safari Mask icon, it seems to work fine with just `favicon.png` (no SVG support).
- Remove Fluid Icon. It only served Firefox and SVG works just fine there.
- Update customization instructions.
- Update README.md to use SVG icon, increase logo size and center it and badges.

* Update README_ZH.md

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

* Update README_ZH.md

Co-authored-by: 6543 <6543@obermui.de>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>

docs/content/doc/advanced/customizing-gitea.en-us.md

@@ -59,11 +59,20 @@ the url `http://gitea.domain.tld/image.png`.
 
 ## Changing the default logo
 
-To automatically update custom logo png and svg files replace `assets/logo.svg` and run `make generate-images`. This will update the user-designated logo files served in `public/img`. Alternatively, you can manually update each `logo-X.png` and `logo.svg` file in `public/img`.
+To build a custom logo replace `assets/logo.svg` and run `make generate-images`. This will update
+these customizable logo files which you can then place in `custom/public/img` on your server:
+
+- `public/img/logo.svg`
+- `public/img/logo.png`
+- `public/img/favicon.png`
+- `public/img/avatar_default.png`
+- `public/img/apple-touch-icon.png`
 
 ## Changing the default avatar
 
-Place the png image at the following path: `custom/public/img/avatar_default.png`
+Either generate it via above method or place the png image at the following path:
+
+- `custom/public/img/avatar_default.png`
 
 ## Customizing Gitea pages and resources