Improve/fix the local development experience

[florian-lefebvre]

Context: https://discord.com/channels/895029566685462578/1027675046602362890

Currently, developing the docs is impossible :

• No docs about how to get started etc
• Styles are quite broken
• Not HMR when it comes to md content

I understand some points are related to the fact that the app is available at /api but still, routing is broken. This prevents quite some contributions to docs after improvements made to the node package (see novuhq/novu#1315).

cc @scopsy @andrewgolovanov