Add user email as webhook jinja2 context

[netgab]

NetBox version
v4.0.8

Feature type
New functionality

Proposed functionality
Currently NetBox support the webhook jinja2 contexts, which are documented here: https://netboxlabs.com/docs/netbox/en/stable/integrations/webhooks/#available-context

It could be desired, that an eMail is sent to the user, which triggered the webhook, within the triggered webhook logic.
The only documented attribute to get the user context is username (jinja2 expression {{ username }}.

As NetBox knows the user eMail as well (in most cases) (see user profile > eMail), the additional jinja2 context user_email could be helpful.