Send admins a notification when a `Hired::Form` is created

[joemasilotti]

A PR addressing this issue should:

• Create a new notification, Admin::NewHiredFormNotification when a Hired::Form is created
• #title - A developer was hired via RailsDevs!
• #url - admin_hired_form_path
• A new mailer on AdminMailer (and preview) should also be added

Feel free to use placeholder copy and I can tweak it when a PR is submitted.

[sarvaiyanidhi]

Hi @joemasilotti Would like to take up this feature.. can you please assign it to me?

[joemasilotti]

Sure thing – all yours @sarvaiyanidhi!

[joemasilotti]

Closed via #625.