Manually deploy Amplify Gen2 project

### Is this related to a new or existing framework?

_No response_

### Is this related to a new or existing API?

_No response_

### Is this related to another service?

Amplify Hosting

### Describe the feature you'd like to request

I'd like to deploy a new Amplify Gen2 project without using the Amplify UI in the AWS Console to connect to a git provider. My project is in self-hosted Gitlab and there is no external access.

### Describe the solution you'd like

I'd like to docs to provide a description of how to perform a first-time deploy of a Gen2 project without connecting to an external git provider, whether it is fairly easy via ```npx amplify``` or more difficult via AWS SDK.

### Describe alternatives you've considered

I have considered temporarily putting my code on a different service provider in order to deploy - however, if I did so, I am unsure how I would change the configuration to only go back to manual deploys afterwards.

### Additional context

_No response_

### Is this something that you'd be interested in working on?

- [ ] 👋 I may be able to implement this feature request
- [ ] ⚠️ This feature might incur a breaking change