First draft of implementation (#1)

* First draft of implementation

Readme will follow

* Rename id.

* Exclude `commons-io` to disable build warnings

* Simplify metrics and add documentation

src/test/java/io/kokuwa/keycloak/metrics/prometheus/PrometheusMetric.java

@@ -0,0 +1,13 @@
+package io.kokuwa.keycloak.metrics.prometheus;
+
+import java.util.Map;
+
+/**
+ * Represents a parsed Prometheus line.
+ *
+ * @author Stephan Schnabel
+ * @param name  Metric name
+ * @param tags  Tags for this metriv value
+ * @param value Metric value
+ */
+public record PrometheusMetric(String name, Map<String, String> tags, Double value) {}