docs(minecraft-router): helmify docs (#32755)

**Description**
<!--
New helmify docs for minecraft-router. mc-router is replaced, so hereby
new docs.
-->
⚒️ Fixes  # <!--(issue)-->

**⚙️ Type of change**

- [ ] ⚙️ Feature/App addition
- [ ] 🪛 Bugfix
- [ ] ⚠️ Breaking change (fix or feature that would cause existing
functionality to not work as expected)
- [ ] 🔃 Refactor of current code
- [x] 📜 Documentation Changes

**🧪 How Has This Been Tested?**
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**📃 Notes:**
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**✔️ Checklist:**

- [ ] ⚖️ My code follows the style guidelines of this project
- [ ] 👀 I have performed a self-review of my own code
- [ ] #️⃣ I have commented my code, particularly in hard-to-understand
areas
- [x] 📄 I have made changes to the documentation
- [ ] 🧪 I have added tests to this description that prove my fix is
effective or that my feature works
- [ ] ⬆️ I increased versions for any altered app according to semantic
versioning
- [x] I made sure the title starts with `feat(chart-name):`,
`fix(chart-name):`, `chore(chart-name):`, `docs(chart-name):` or
`fix(docs):`

**➕ App addition**

If this PR is an app addition please make sure you have done the
following.

- [ ] 🖼️ I have added an icon in the Chart's root directory called
`icon.png`

---

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---------

Signed-off-by: Alfred Göppel <43101280+alfi0812@users.noreply.github.com>
Co-authored-by: Alfred Göppel <43101280+alfi0812@users.noreply.github.com>

charts/stable/minecraft-router/docs/how-to.md

@@ -0,0 +1,20 @@
+---
+title: Minecraft-Server How To
+---
+
+When you have multiple Java Minecraft-Servers running and you want to open for all the standard 25565 port. Minecraft-Router is the solution.
+The correct minecraft server will be chosed based upon which URL is used to connect.
+
+Default server can be given in the case an unknown URL is detected.
+
+More information about linking charts and Cluster Internal Domain can be found in the common documentation.
+Example deployment, used with Cluster Internal Domain names:
+
+```yaml
+mcrouter:
+   default: minecraft-java.minecraft-java.svc.cluster.local:25565
+    mappings:
+      - ${SERVER1_URL}=minecraft-java.minecraft-java.svc.cluster.local:25565
+      - ${SERVER2_URL}=truecharts-mcserver-minecraft-java.truecharts-mcserver.svc.cluster.local:25565
+      - ${SERVER3_URL}=kidsplayground-server-minecraft-java.kidsplayground-server.svc.cluster.local:25565
+````