Add-ons installation: correct links to mqtt doc (#719)

Signed-off-by: Yannick Schaus <github@schaus.net>

configuration/addons.md

@@ -45,10 +45,10 @@ openhab-binding-network                   │ 2.2.0            │          │
 According to the [naming convention for bundles](/docs/administration/bundles.html#naming-convention-for-bundles) the *id* for the shown example is *network*.
 
 Another way to find the correct `id` is to look at the URL of the add-on documentation page.
-For example the url for the [mqtt Binding documentation](/docs/addons/bindings/mqtt1/readme.html) is
+For example the url for the [mqtt Binding documentation](/docs/addons/bindings/mqtt1/) is
 
 ```text
-https://docs.openhab.org/addons/bindings/mqtt1/readme.html
+https://www.openhab.org/addons/bindings/mqtt1/
 ```
 
 In this case, the `id` would be "mqtt1".
@@ -95,4 +95,4 @@ One way of retrieving those files is mentiones above in the openHAB console part
 
 Place the `.jar` file in the `add-ons` folder on the machine you are running openHAB on.
 As described already for the addons.cfg option, the path is depending on your installation.
-Place the .jar file in the folder Additional add-on files as described in File Locations ([Linux](/docs/installation/linux.html#file-locations), [Windows](/docs/installation/windows.html#file-locations) or [macOS](/docs/installation/macosx.html#file-locations)).
+Place the .jar file in the folder Additional add-on files as described in File Locations ([Linux](/docs/installation/linux.html#file-locations), [Windows](/docs/installation/windows.html#file-locations) or [macOS](/docs/installation/macosx.html#file-locations)).