Add support for slack app (bot) instead of incomingwebhook

[sushovan23]

Is your feature request related to a problem? Please describe.
Slack has made incoming webhooks deprecated and suggesting to use only slack app n chat.write api to send notifications to slack.

Describe the solution you'd like
add support for slack bot along with incoming webhook url. Allow specifying bot token and channel id.

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context or screenshots about the feature request here.