Add v2 Remote Config Triggers

[colerogers]

Adds remote config triggers to CF3v2

import { onConfigUpdated } from 'firebase-functions/v2/remoteConfig';

export const fn = onConfigUpdated((event) => { console.log("hello world"); });

[TheIronDev]

LGTM!

[taeold]

Loving the doc comments. Do you want to mark these triggers as @Alpha until we have samples/docs/CLI support merged and released?

[taeold]

One more thing - do you want to add integration test target for this (in this PR or later in another PR).

[colerogers]

@taeold - added the @alpha tags & since this change requires CLI changes to be released, I'll follow up with a int test in another PR