docs(bitmagnet) add Scale App Installation docs (#18563)

**Description**
Add Scale App Installation 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

**🧪 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
- [ ] 📄 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 added an icon in the Chart's root directory called
`icon.png`

---

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charts/stable/bitmagnet/docs/installation_notes.md

@@ -0,0 +1,9 @@
+---
+title: Scale App Installation
+---
+
+To effortlessly kickstart your journey with bitmagnet, integrate the [TrueCharts catalog](https://truecharts.org/manual/SCALE/guides/getting-started#adding-truecharts) and proceed with app installation on TrueNAS Scale.
+
+Optionally, you can configure the `TMDB API Key` by following the guidelines outlined [here](https://bitmagnet.io/setup/configuration.html#obtaining-a-tmdb-api-key).
+
+Worth noting, the PostgreSQL database is seamlessly configured and installed alongside the app. Just ensure to meticulously adhere to the getting started guide, installing all the recommended operators before initiating the app installation process.