examples: add example for a simple rest server with a small api

show how to generally start a daemon that serves a rest api + index page

api calls are (prefixed with either /api2/json or /api2/extjs):
/		GET	listing
/ping		GET	returns "pong"
/items		GET	lists existing items
		POST	lets user create new items
/items/{id}	GET	returns the content of a single item
		PUT	updates an item
		DELETE	deletes an item

Contains a small dummy user/authinfo

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>

proxmox-rest-server/Cargo.toml

@@ -5,6 +5,11 @@ authors = ["Proxmox Support Team <support@proxmox.com>"]
 edition = "2018"
 description = "REST server implementation"
 
+# for example
+[dev-dependencies]
+proxmox = { version = "0.13", features = ["router","api-macro"] }
+tokio = { version = "1.6", features = [ "rt-multi-thread", "signal", "process" ] }
+
 [dependencies]
 anyhow = "1.0"
 futures = "0.3"