[feat] engines: add devicons engine

- official website: https://devicon.dev/
- the engine contains a lot of icons of popular software frameworks (e.g. pytest),
so they could for example be useful for visualizing a diagram of the tech stack used in an app

searx/settings.yml

@@ -736,6 +736,11 @@ engines:
     shortcut: da
     timeout: 3.0
 
+  - name: devicons
+    engine: devicons
+    shortcut: di
+    timeout: 3.0
+
   - name: ddg definitions
     engine: duckduckgo_definitions
     shortcut: ddd