docs(firezone): add dns only image (#14350)

**Description**
Adds image showing DNS only for cloudflare.

⚒️ 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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Co-authored-by: StevenMcElligott <[email protected]>

charts/stable/firezone/docs/installation_notes.md

@@ -17,7 +17,7 @@ How to setup FireZone.
 Most configuration can be left default here but some you want to change.
 
 - Set `Default Client MTU` to a size that works for _your_ network, default is 1280.
-- Set `Client Endpoint` to any of the following, if using a domain it needs to resolve to your public IP so it can not be proxied on CloudFlare.
+- Set `Client Endpoint` to any of the following, if using a domain it needs to resolve to your public IP so it can not be proxied on CloudFlare. ![firezone-dns-only](./img/firezone-dns-only.png)
 
   - publicIP:WG_PORT
   - app.domain.tld:WG_PORT