feat: Add F-Droid QR Code to README - fixes https://gitlab.com/ironfox-oss/IronFox/-/issues/69

Signed-off-by: celenity <celenity@celenity.dev>

README.md

@@ -1,10 +1,12 @@
 # IronFox
 
-<p align="center">
-    <img src="assets/ironfox.png"
+<div align="center">
+
+<img src="assets/ironfox.png"
         alt="IronFox"
         height="200">
-</p>
+
+</div>
 
 <div align="center">
 
@@ -20,6 +22,15 @@
 
 </div>
 
+<div align="center">
+
+**F-Droid QR Code**:
+[<img src="assets/f-droid_qr.png"
+    alt="Get it on F-Droid"
+    height="300">](fdroidrepos://fdroid.ironfoxoss.org/fdroid/repo?fingerprint=C5E291B5A571F9C8CD9A9799C2C94E02EC9703948893F2CA756D67B94204F904)
+
+</div>
+
 ---
 
 IronFox is a fork of [Divested Computing Group](https://divested.dev/)'s [Mull Browser](https://divestos.org/pages/our_apps#mull), based on [Mozilla Firefox](https://www.mozilla.org/firefox/). **Our goal is to continue the legacy of Mull by providing a free and open source, privacy and security-oriented web browser for daily use.**