Improve documentation and onboarding guide

[ParadauxIO]

It's possible non technical users will stumble across this so the README should be more hand-holdy. It would also be nice to include some screenshots of the bot in action in various sitatuins

• Responding randomly
• Responding on mention
• Responding in dedicated channel
• Responding on use of a wake word

[ParadauxIO]

This should include fixing references to configuration to be the new HOCON format rather than the old JSON format

[ayushmaanshrotriya]

will do