Fix nmpolicy document

Signed-off-by: Gris Ge <fge@redhat.com>

Author: cathay4t

nmpolicy/examples.md

@@ -0,0 +1,39 @@
+# Set all linux bridges down
+
+### policy
+```yaml
+capture:
+  linux-bridges: interfaces.type=="linux-bridge"
+  linux-bridges-down: capture.linux-bridges | interfaces.state:="down"
+desired:
+  interfaces: "{{ capture.linux-bridges-down.interfaces }}"
+```
+
+### current state
+```yaml
+interfaces:
+- name: eth0
+  type: ethernet
+- name: br1
+  type: linux-bridge
+  state: up
+- name: br2
+  type: linux-bridge
+  state: up
+- name: br3
+  type: linux-bridge
+  state: up
+```
+
+### generated state
+```yaml
+interfaces:
+- name: br1
+  type: linux-bridge
+  state: down
+- name: br2
+  type: linux-bridge
+  state: down
+- name: br3
+  type: linux-bridge
+  state: down