docs: Add logger documentation

wiki/logger.md

@@ -0,0 +1,20 @@
+# Logger
+
+As any web application, verdaccio has a customisable build-in logger. You can define a multiple types of outputs.
+
+```yaml
+logs:
+  # console output
+  - {type: stdout, format: pretty, level: http}
+  # file output
+  - {type: file, path: verdaccio.log, level: info}
+```
+
+### Configuration
+
+Property | Type | Required | Example | Support | Description 
+--- | --- | --- | --- | --- | --- 
+type |  string | No | [stdout, file] | all | define the output
+path | string | No | verdaccio.log | all | if type is file, define the location of that file 
+format | string | No | [pretty, pretty-timestamped] | all | output format
+level | string | No | [fatal, error, warn, http, info, debug, trace] | all | verbose level