fr: add different stages (periods) of proposal notification by bot

[tohrxyz]

The bot should notify the channel of a proposal in several stages:

• before the voting starts -> notify users when it will start
• after it started -> tell users it started and how much time they have left to vote
• several times during the proposal lifetime (once a day? every 2 days?)
• day before it ends
• hour before it ends
• 10 minutes before it ends
• notify users that it has ended and show the results and what will be executed

All of these stages are up for a debate, not sure if all are required. Probably it depends on the severity and content of a proposal and should be configurable during start of this bot.