Add metrics to the config sample and schema

config/config.sample.yaml

@@ -104,3 +104,8 @@ ghosts:
     nickPattern: ":nick"
     # Pattern for the ghosts username, available is :username, :tag and :id
     usernamePattern: ":username#:tag"
+# Prometheus-compatible metrics endpoint
+metrics:
+    enabled: false
+    port: 9001
+    host: "localhost"
\ No newline at end of file

config/config.schema.yaml

@@ -124,3 +124,12 @@ properties:
                 type: "string"
             usernamePattern:
                 type: "string"
+    metrics:
+        type: "object"
+        properties:
+            enabled:
+                type: "boolean"
+            port:
+                type: "number"
+            host:
+                type: "string"