feat(cpa): create project from example using --example CLI arg (#10172)

Adds the ability to create a project using an existing in the Payload
repo example through `create-payload-app`:

For example:
`pnpx create-payload-app --example custom-server` - creates a project
from the
[custom-server](https://github.com/payloadcms/payload/tree/main/examples/custom-server)
example.

This is much easier and faster then downloading the whole repo and
copying the example to another folder.
Note that we don't configure the payload config with the storage / DB
adapter there because examples can be very specific.

examples/draft-preview/README.md

@@ -6,15 +6,14 @@ The [Payload Draft Preview Example](https://github.com/payloadcms/payload/tree/m
 
 To spin up this example locally, follow these steps:
 
-1. Clone this repo
-2. `cd` into this directory and run `pnpm i --ignore-workspace`\*, `yarn`, or `npm install`
+1. Run the following command to create a project from the example:
 
-   > \*If you are running using pnpm within the Payload Monorepo, the `--ignore-workspace` flag is needed so that pnpm generates a lockfile in this example's directory despite the fact that one exists in root.
+- `npx create-payload-app --example draft-preview`
 
-3. `cp .env.example .env` to copy the example environment variables
-4. `pnpm dev`, `yarn dev` or `npm run dev` to start the server
-5. `open http://localhost:3000/admin` to access the admin panel
-6. Login with email `demo@payloadcms.com` and password `demo`
+2. `cp .env.example .env` to copy the example environment variables
+3. `pnpm dev`, `yarn dev` or `npm run dev` to start the server
+4. `open http://localhost:3000/admin` to access the admin panel
+5. Login with email `demo@payloadcms.com` and password `demo`
 
 That's it! Changes made in `./src` will be reflected in your app. See the [Development](#development) section for more details.