Fix image links

docs/usage/upgrade_guide.md

@@ -9,16 +9,16 @@ In the old versions, autocomplete was only possible through the use of the autoc
 Nowadays, there are many possible solutions for autocomplete:
 
 1. **Prefix Autocomplete**  
-  <img src="/assets/images/autocomplete_new_prefix.png" alt="New Autocomplete Example With Prefix" style="max-width: 50%">  
+  <img src="../assets/images/autocomplete_new_prefix.png" alt="New Autocomplete Example With Prefix" style="max-width: 50%">  
   When typing an @ or # with the name of a nick or channel afterwards, Quasseldroid automatically recommends
   You can also configure this to always autocomplete even without prefix
 
 2. **Double-Tap to Autocomplete**  
-  <img src="/assets/images/autocomplete_new_doubletap.png" alt="New Autocomplete Example With Doubletap" style="max-width: 50%">  
+  <img src="../assets/images/autocomplete_new_doubletap.png" alt="New Autocomplete Example With Doubletap" style="max-width: 50%">  
   When typing a name, you can double-tap the input box to autocomplete the name
 
 3. **Autocomplete Button**  
-  <img src="/assets/images/autocomplete_new_button.png" alt="New Autocomplete Example With Button" style="max-width: 50%">  
+  <img src="../assets/images/autocomplete_new_button.png" alt="New Autocomplete Example With Button" style="max-width: 50%">  
   Of course, the good old autocomplete button can be re-enabled again, too.
 
 ## Avatars