v1.19.0-ls77

LinuxServer Changes:

Add libffi-dev to allow building of python cryptography lib.
healthchecks Changes:

Improvements

• Add tighter parameter checks in hc.front.views.serve_doc
• Update OpsGenie instructions (#450)
• Update the email notification template to include more check and last ping details
• Improve the crontab snippet in the "Check Details" page (#465)
• Add Signal integration (#428)
• Change Zulip onboarding, ask for the zuliprc file (#202)
• Add a section in Docs about running self-hosted instances
• Add experimental Dockerfile and docker-compose.yml
• Add rate limiting for Pushover notifications (6 notifications / user / minute)
• Add support for disabling specific integration types (#471)

Bug Fixes

• Fix unwanted HTML escaping in SMS and WhatsApp notifications
• Fix a crash when adding an integration for an empty Trello account
• Change icon CSS class prefix to 'ic-' to work around Fanboy's filter list