add collection package to doc

Author: NikolasK-source

docs/index.md

@@ -76,8 +76,14 @@ This option cannot be used with flatpaks.
 setcap 'cap_net_bind_service=+ep' /path/to/binary
 ```
 
+## Install
 
-## Using the Flatpak package
+### Using the Modbus Collection Flapak Package: Shared Memory Modbus (recommended)
+[SHM-Modbus](https://nikolask-source.github.io/SHM_Modbus/) is a collection of the shared memory modbus tools.
+It is available as flatpak and published on flathub as ```network.koesling.shm-modbs```.
+
+
+### Using the Standalone Flatpak Package
 The flatpak package can be installed via the .flatpak file.
 This can be downloaded from the GitHub [projects release page](https://github.com/NikolasK-source/modbus_tcp_client_shm/releases):
 
@@ -94,7 +100,7 @@ To enable calling with ```modbus-tcp-client-shm``` [this script](https://gist.gi
 In order to be executable everywhere, the path in which the script is placed must be in the ```PATH``` environment variable.
 
 
-## Build from Source
+### Build from Source
 
 The following packages are required for building the application:
 - cmake