Update README.md

WU731642061 · web-flow · commit 99669f8061cc · 2018-03-08T17:20:34.000+08:00
In example part,   
vapid_claims={
                "sub": "YourNameHere@example.org",
            }
It will lead to an error which lacks "mailto" fields.
diff --git a/README.md b/README.md
@@ -98,7 +98,7 @@ try:
         data="Mary had a little lamb, with a nice mint jelly",
         vapid_private_key="path/to/vapid_private.pem",
         vapid_claims={
-                "sub": "YourNameHere@example.org",
+                "sub": "mailto:YourNameHere@example.org",
             }
     )
 except WebPushException as ex:

Original file line number	Diff line number	Diff line change
`@@ -98,7 +98,7 @@ try:`
`98`	`98`	`data="Mary had a little lamb, with a nice mint jelly",`
`99`	`99`	`vapid_private_key="path/to/vapid_private.pem",`
`100`	`100`	`vapid_claims={`
`101`		`- "sub": "[email protected]",`
	`101`	`+ "sub": "mailto:[email protected]",`
`102`	`102`	`}`
`103`	`103`	`)`
`104`	`104`	`except WebPushException as ex:`