client side validation for `url` and `status report` fields

When you submit a HappyChat request for WooCommerce.com, a site url and status report are required fields. The format of these fields is tricky and it could be frustrating for users as the server-side validation takes time, and blocks the support request. Adding some basic client-side validation could make the experience of reaching out for help a little smoother.

#### How to reproduce
- Get HappyChat up in WooCommerce mode (this may apply to other modes, not sure if these fields are woo-specific).
- You're feeling stressed out, need some help, and in a hurry. Type some random characters in the `url` and `status report` fields so you can get your support request underway.
- Click `Submit Request` ..
- .. wait ..
- `System Status Report is invalid or unsupported` or other `computer says no` responses, dang it!

Start at the HappyChat request form in WooCommerce mode and trace how the `url` and `status report` fields are submitted. Confirm the expected formats from the server responses, then ensure invalid values are identified before submission and that valid requests can still proceed.

Written by the indexing model from the issue text.