feat: Gemini (#135)

* gemini setup for api check

* docs and tests, todo small fix

* fixed api checks, better tests

* bump version

Author: erhant

.env.example

@@ -25,6 +25,9 @@ DKN_BOOTSTRAP_NODES=
 ## Open AI (if used, required) ##
 OPENAI_API_KEY=
 
+## Gemini (if used, required) ##
+GEMINI_API_KEY=
+
 ## Ollama (if used, optional) ##
 # do not change this, it is used by Docker
 OLLAMA_HOST=http://host.docker.internal