Minor fixes

[0x2142]

Bunch of misc fixes/adjustments/enhancements:

• Update docs regarding Frigate server config (Documentation of server address is incomplete #56)
• Fix default web API query interval (Web API default interval is actually 0 #55)
• Add new public_url config item for Frigate (Feature: Support Basic authentication and Bearer Token authorization for a connection to Frigate server #52)
• Add startup check to ensure Frigate is reachable & validate configured IP/hostname/URL (Documentation of server address is incomplete #56)
• Fix 0% label scores when using web API to query events (Incomplete notifications in Telegram #54)
• Remove markdown dependency, which is no longer needed after implementing templates for notifications (Notif templates #59)

This should wrap up work for version 0.2.8 🥳