Write "Going into production" docs / rewrite of deployment docs

[infomiho]

Users deploying Wasp apps sometimes get stuck and they report it on our Discord. Some of the common themes:

• env variables are missing
• CORS is not working as expected
• database migrations are misunderstood
• Wasp app building blocks are misunderstood
• client routing is misunderstood

We cover a lot of topics in our docs (manual deployment, deploying using the Wasp CLI, env variables, some general Prisma advice) but we don't have the "going into production" topic covered from start to finish.

Here's a rough outline on what I plan to write:

One of the moves is recommended by our Discord member: moving the deployment docs on the top level. I agree with that, since all users will want to deploy, it shouldn't be hidden away in the Advanced section.

Ideally, we'd make a new top level category Deployment with the following rough outline:

Deployment/
├─ Wasp building blocks
├─ Env variables
├─ Database and schema migrations
├─ Deployment methods/
│  ├─ PaaS options
│  ├─ Self-hosting 
│  ├─ Static hosting for the client
├─ CI/CD setup
├─ Extras/
│  ├─ Using a custom domain
│  ├─ What can Wasp handle in production
│  ├─ DDoS and CDN