Implement a configuration form for setting up Snyk alerts for new issues

[carwin]

Abstract:
The config form should contain a multi-select list of channels, issue severity levels, and snyk projects as well as some kind of automatic Webhook registration with Snyk (Users shouldn't have to go to the CLI to register a webhook and then come back to configure the filers)

Tasks:

• Create Config form in App Home layer
• Implement some kind of "Add another" option for the form - this would cover use cases where different projects need to send alerts to different channels, etc...
• Implement "Register Webhook" button