Add documentation for 3rd party Rspamd modules (#575)

* English documentation for adding 3rd party modules to Rspamd

* Added German translations, thanks to @MAGICCC

---------

Co-authored-by: SnailShea <shea@vulpes.club>

docs/manual-guides/Rspamd/u_e-rspamd.de.md

@@ -346,3 +346,37 @@ Starten Sie anschließend Rspamd neu:
     ``` bash
     docker-compose restart rspamd-mailcow
     ```
+
+## Hinzufügen von Rspamd Modulen
+
+Laden Sie das Modul herunter und speichern Sie es in folgenden Pfad ab: `data/conf/rspamd/plugins.d/`.
+
+Danach müssen Sie die Konfigurationsparameter des Modules in `data/conf/rspamd/rspamd.conf.local` hinzufügen.
+Falls das Modul `my_plugin.lua` heißt, sollte die Datei wie folgt aussehen:
+
+```
+# rspamd.conf.local  
+my_plugin {
+    some_setting = "some value";
+}
+```
+
+Falls Ihr Modul keine zusätzlichen Konfigurationen benötigt, reicht es aus einen leeren Konfigurationsblock hinzuzufügen. Wie im folgenden Beispiel zu sehen:
+
+```
+# rspamd.conf.local  
+my_plugin { }
+```
+
+Falls Sie keinen Konfigurationsblock hinzufügen, dann wird das Modul automatisch deaktiviert und im Logfile des rspamd-mailcow Containers sehen Sie folgende Nachricht:
+
+
+```
+mailcowdockerized-rspamd-mailcow-1  | 2023-05-20 14:01:32 #1(main) <sh6j9z>; cfg; rspamd_config_is_module_enabled: lua module my_plugin is enabled but has not been configured
+mailcowdockerized-rspamd-mailcow-1  | 2023-05-20 14:01:32 #1(main) <sh6j9z>; cfg; rspamd_config_is_module_enabled: my_plugin disabling unconfigured lua module
+```
+
+Falls Sie das Modul erfolgreich konfiguiert haben, dann sollte das Logfile des rspamd-mailcow Containers wie folgt aussehen:
+
+```
+mailcowdockerized-rspamd-mailcow-1  | 2023-05-20 14:04:50 #1(main) <8ayxpf>; cfg; rspamd_init_lua_filters: init lua module my_plugin from /etc/rspamd/plugins.d//my_plugin.lua; digest: 5cb88961e5

docs/manual-guides/Rspamd/u_e-rspamd.en.md

@@ -352,3 +352,37 @@ Restart Rspamd afterwards:
     ``` bash
     docker-compose restart rspamd-mailcow
     ```
+
+## Adding Rspamd modules
+
+Download the module and save it in the following path: `data/conf/rspamd/plugins.d/`.
+
+Next, add any necessary configuration for your module to `data/conf/rspamd/rspamd.conf.local`. \
+If you have a module named `my_plugin.lua`, configuration might look like the following:
+
+```
+# rspamd.conf.local  
+my_plugin {
+    some_setting = "some value";
+}
+```
+
+If your module does not require any additional configuration, simply add an empty configuration block, for example:
+
+```
+# rspamd.conf.local  
+my_plugin { }
+```
+
+If you do not add a configuration block, the module will be automatically disabled, and the rspamd-mailcow container log will contain a message such as:
+
+```
+mailcowdockerized-rspamd-mailcow-1  | 2023-05-20 14:01:32 #1(main) <sh6j9z>; cfg; rspamd_config_is_module_enabled: lua module my_plugin is enabled but has not been configured
+mailcowdockerized-rspamd-mailcow-1  | 2023-05-20 14:01:32 #1(main) <sh6j9z>; cfg; rspamd_config_is_module_enabled: my_plugin disabling unconfigured lua module
+```
+
+If you have successfully configured your module, the rspamd-mailcow container logs should show:
+
+```
+mailcowdockerized-rspamd-mailcow-1  | 2023-05-20 14:04:50 #1(main) <8ayxpf>; cfg; rspamd_init_lua_filters: init lua module my_plugin from /etc/rspamd/plugins.d//my_plugin.lua; digest: 5cb88961e5
+```