Consider environment variables during app.ini creation (#298)

This PR improves the handling and injection into _app.ini_ of user defined environment variables via env-to-ini script.

Fixes #297

Co-authored-by: Lucas Hahn <lucas.hahn@novum-rgi.de>
Reviewed-on: https://gitea.com/gitea/helm-chart/pulls/298
Reviewed-by: justusbunsi <justusbunsi@noreply.gitea.io>
Reviewed-by: 6543 <6543@obermui.de>

values.yaml

@@ -213,6 +213,8 @@ gitea:
   #   - configMap:
   #       name: gitea-app-ini-plaintext
 
+  additionalConfigFromEnvs: []
+
   podAnnotations: {}
 
   # Modify the liveness probe for your needs or completely disable it by commenting out.