Add note about callbackMethod

Author: knolleary

README.md

@@ -23,6 +23,6 @@ First time you run jeykll you need to do bundle install 1st for the dependencies
 
     cd node-red.github.io
     bundle install
-    jekyll serve -w
+    bundle exec jekyll serve -w
 
 Once the site is built and running you can preview it at [`http://127.0.0.1:4000/`](http://127.0.0.1:4000/).

docs/user-guide/runtime/securing-node-red.md

@@ -197,7 +197,7 @@ The `strategy` property takes the following options:
  - `label`/`icon` - used on the login page. `icon` can be any FontAwesome icon name.
  - `options` - an options object passed to the passport strategy when it is created.
    Refer to the strategy's own documentation for what it requires. See below for a
-   node on the `callbackURL`.
+   note on the `callbackURL` and `callbackMethod`.
  - `verify` - the verify function used by the strategy. It must call `done` with
    a user profile as the second argument if the user is valid. This is expected
    to have a `username` property that is used to check against the list of valid
@@ -209,6 +209,8 @@ redirect to following an auth attempt. It must be the URL of your Node-RED edito
 with `/auth/strategy/callback` added to the path. For example, if you access the
 editor at `http://localhost:1880`, you would use `http://localhost:1880/auth/strategy/callback`.
 
+By default, the `callbackURL` will listen for `GET` requests. To use `POST` requests
+instead, set `callbackMethod` to `POST`.
 
 #### Setting a default user