Add VSCodium

"binary releases of VS Code without MS branding/telemetry/licensing"

* Homepage: https://vscodium.com/
* Source Code: https://github.com/VSCodium/vscodium

Since Visual Studio Code is present, might as well add the Free/Libre
version of it.

Logo by @Pittan:
#141 (comment)

Based on:
https://github.com/VSCodium/vscodium/blob/cb5e22e005a1e3373f5e0ee9bb79d182587db2df/src/resources/linux/code.png

Co-authored-by: pittan <amon.keishima@pittankopta.net>

Author: 2 people

index.html

@@ -187,6 +187,7 @@ <h3>Editor</h3>
     <li><a href="https://github.com/editorconfig/editorconfig-textadept#readme"><img src="logos/textadept.png" alt="Textadept"><span>Textadept</span></a></li>
     <li><a href="https://github.com/Mr0grog/editorconfig-textmate#readme"><img src="logos/textmate.png" alt="TextMate"><span>TextMate</span></a></li>
     <li><a href="https://github.com/editorconfig/editorconfig-vim#readme"><img src="logos/vim.png" alt="Vim"><span>Vim</span></a></li>
+    <li><a href="https://open-vsx.org/extension/EditorConfig/EditorConfig"><img src="logos/vscodium.png" alt="VSCodium"><span>VSCodium</span></a></li>
     <li><a href="https://marketplace.visualstudio.com/items?itemName=EditorConfig.EditorConfig"><img src="logos/visualstudio-code.png" alt="Visual Studio Code"><span>Visual Studio Code</span></a></li>
   </ul>