git: Added flatpak link to install guide

Author: WerWolv

INSTALL.md

@@ -40,10 +40,13 @@ ImHex is also available on various package managers. The officially supported on
 - **Fedora**
   - [imhex](https://src.fedoraproject.org/rpms/imhex/) (Thanks to @jonathanspw)
     - `dnf install imhex`
+- **Flatpak**
+  - [net.werwolv.Imhex](https://flathub.org/apps/details/net.werwolv.ImHex) (Thanks to @Mailaender)
+    - `flatpak install flathub net.werwolv.ImHex`
 
 ### Available on other package managers
 
 Packages that aren't explicitly mentioned above are not officially supported but they will most likely still work.
 Contact the maintainer of the package if you have any issues.
 
-[![Packaging status](https://repology.org/badge/vertical-allrepos/imhex.svg)](https://repology.org/project/imhex/versions)
+[![Packaging status](https://repology.org/badge/vertical-allrepos/imhex.svg)](https://repology.org/project/imhex/versions)