gnmic: add page and subpages (#8367)

* gnmic - add

* Change file extension

* Fix newlines

* update gnmic pages and add gnmic sub alias

* fix link

* add period

* fix missing punctuation

* fix ip:port formatting

* Implemented @adrienthebo suggestions

* missing period

* @EmilySeville7cfg suggestions

* remove --insecure and write out sub

pages/common/gnmic-get.md

@@ -0,0 +1,20 @@
+# gnmic get
+
+> Get a snapshot of a gnmi network device operation data.
+> More information: <https://gnmic.kmrd.dev/cmd/get>.
+
+- Get a snapshot of the device state at a specific path:
+
+`gnmic --address {{ip:port}} get --path {{path}}`
+
+- Query the device state at multiple paths:
+
+`gnmic -a {{ip:port}} get --path {{path1}} --path {{path2}}`
+
+- Query the device state at multiple paths with a common prefix:
+
+`gnmic -a {{ip:port}} get --prefix {{prefix}} --path {{path1}} --path {{path2}}`
+
+- Query the device state and specify reponse encoding (json_ietf):
+
+`gnmic -a {{ip:port}} get --path {{path}} --encoding json_ietf`