Account Activity API add subscription resource url updates

[steffes]

Last week the documentation for Account Activity API was updated.

When adding a subscription to a webhook, you don't need the webhook ID for the Standard Account Activity API like the one in

https://github.com/twitterdev/twitter-webhook-boilerplate-node/blob/e6ff99bc4ea548f8cef10f8f3a757710bab6aea1/example_scripts/webhook_management/add-subscription.js#L21

I was able to add a subscription via twurl
twurl -X POST /1.1/account_activity/all/env-beta/subscriptions.json

The issue is that the Enterprise Account Activity API still has :webhook_id in its resource url. But the url in add-subscription.js would still need to be updated because the resource for the enterprise API is
https://api.twitter.com/1.1/account_activity/webhooks/:webhook_id/subscriptions/all.json