Edit Discord Badge (#28188)

Use white Discord icon. Label the badge as "Discord". Use the official
Discord logo's color value of 5865F2.

README.md

@@ -10,7 +10,7 @@
     <img src="https://github.com/go-gitea/gitea/actions/workflows/release-nightly.yml/badge.svg?branch=main">
   </a>
   <a href="https://discord.gg/Gitea" title="Join the Discord chat at https://discord.gg/Gitea">
-    <img src="https://img.shields.io/discord/322538954119184384.svg">
+    <img src="https://img.shields.io/discord/322538954119184384.svg?logo=discord&logoColor=white&label=Discord&color=5865F2">
   </a>
   <a href="https://app.codecov.io/gh/go-gitea/gitea" title="Codecov">
     <img src="https://codecov.io/gh/go-gitea/gitea/branch/main/graph/badge.svg">