Add new channel entry for 'restaurant'

[xelphyr]

Channel Checklist

• [✅] I am a channel manager of the Slack personal channel I am adding.
• [✅] I have added the correct channel_id and my user_id in channels.yml.
• [✅] I have added the slug I want for my channel in channels.yml.
• [✅] I have added valid previous and next redirect URLs in my channel's description (e.g. https://r.sahil.ink/n/slug and https://r.sahil.ink/p/slug - check Slack for other valid options)