add example file for configuring config files using config-file-provider plugin (#724)

demos/config-file-provider/README.md

@@ -0,0 +1,52 @@
+# configure config-file-provider files 
+
+## sample configuration
+
+```yaml
+jenkins: 
+  [...]
+unclassified:
+  globalConfigFiles:
+    configs:
+    - custom:
+        id: custom-test
+        name: DummyCustom1
+        comment: dummy custom 1
+        content: dummy content 1
+    - json:
+        id: json-test
+        name: DummyJsonConfig
+        comment: dummy json config
+        content: |
+          { "dummydata": {"dummyKey": "dummyValue"} }
+    - xml:
+        id: xml-test
+        name: DummyXmlConfig
+        comment: dummy xml config
+        content: <root><dummy test="abc"></dummy></root>
+    - mavenSettings:
+        id: maven-test
+        name: DummySettings
+        comment: dummy settings
+        isReplaceAll: false
+        serverCredentialMappings:
+        - serverId: server1
+          credentialsId: someCredentials1
+        - serverId: server2
+          credentialsId: someCredentials2
+        content: |
+          <settings xmlns="http://maven.apache.org/SETTINGS/1.0.0"
+                    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+                    xsi:schemaLocation="http://maven.apache.org/SETTINGS/1.0.0 http://maven.apache.org/xsd/settings-1.0.0.xsd">
+            <!-- activeProfiles
+             | List of profiles that are active for all builds.
+             |
+            -->
+            <activeProfiles>
+              <activeProfile>alwaysActiveProfile</activeProfile>
+              <activeProfile>anotherAlwaysActiveProfile</activeProfile>
+            </activeProfiles>
+          </settings>
+```
+
+