docs(plex): update install notes (#10556)

**Description**
Added information on changing the port used for Plex.

See -> https://forums.plex.tv/t/change-plex-media-server-port-away-from-32400/115662/5

⚒️ Fixes  # 

**⚙️ 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

**🧪 How Has This Been Tested?**

**📃 Notes:**

**✔️ 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
- [ ] 📄 I have made corresponding changes to the documentation
- [ ] ⚠️ My changes generate no new warnings
- [ ] 🧪 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

**➕ App addition**

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

- [ ] 🪞 I have opened a PR on
[truecharts/containers](https://github.com/truecharts/containers) adding
the container to TrueCharts mirror repo.
- [ ] 🖼️ I have added an icon in the Chart's root directory called
`icon.png`

---

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charts/stable/plex/docs/installation_notes.md

@@ -1,5 +1,9 @@
 # Plex Installation Notes
 
+## Public Port
+
+- The LAN port used by Plex (32400) is hardcoded and cannot be changed. Because of this do not change the port in the Plex app config from 32400. If you need to run Plex on a different public port you will need to setup port forwarding on a router from the public port to 32400 on your server IP. You will also need to change the public port in the remote access section of Plex settings.
+
 ## Transcode Folder
 
 - By default the Plex transcode folder is not configured. The recommend setup is emptyDir.
@@ -31,3 +35,4 @@ Keep in mind that emptyDir's memory counts against the resources defined.
 - This option cannot be enabled until initial plex setup is complete and remote access is enabled and functioning as shown below.
 
 ![remote access](./img/plex-remote-access.png)
+