Add ability to authenticate an endpoint

Write an example for basic auth

manifests/examples/basic-auth/secrets.yaml

+apiVersion: v1
+kind: Secret
+metadata:
+  name: basic-auth
+data:
+  password: dG9vcg== # toor
+  user: YWRtaW4= # admin
+type: Opaque
\ No newline at end of file

manifests/examples/basic-auth/service-monitor.yaml

+apiVersion: monitoring.coreos.com/v1alpha1
+kind: ServiceMonitor
+metadata:
+  labels:
+    k8s-apps: basic-auth-example
+  name: basic-auth-example
+spec:
+  endpoints:
+  - basicAuth:
+      password:
+        key: basic-auth
+        name: password
+      username:
+        key: basic-auth
+        name: user
+    port: metrics
+  namespaceSelector:
+    matchNames:
+    - logging
+  selector:
+    matchLabels:
+      app: myapp
\ No newline at end of file