feat: Add Dockerfile that installs cody from source

[Chickensoupwithrice]

Slack context
Linear ticket

This is just so that we have a reference here for now. We're unblocking
a customer while we integrate a CI pipeline that will publish this
whenever an agent release goes out. That means coping the built files
into this container, rather than using npm. We'll also need to give the
GHA the creds to publish this to Dockerhub.

This handles creation of a docker container, pushed to docker hub, which comes pre-installed with the cody npm package, built from source. Previously a single image was published for a customer under the ccsourcegraph account, but this PR makes the process production ready, and hooks into existing CI actions, under the sourcegraph dockerhub account.

I have chosen not to publish this image given it doesn't currently exist
in the Sourcegraph Dockerhub registry. If the customer demands it, I
could.

Once approved and merged, I'll publish the specific image for 5.5.17 to dockerhub since that CI run has already passed.

Running docker build . -t sourcegraph/cody-cli:5.5.17 from the cody/cli directory will give you a container that has cody installed.

Test plan

> docker run --rm sourcegraph/cody-cli cody --help

Usage: cody [options] [command]

The Cody cli supports running Cody in headless mode and interacting with it via
JSON-RPC. Run `cody chat -m "Hello" to get started.

Options:
  -v, --version   output the version number
  -h, --help      display help for command

Commands:
  auth            Authenticate Cody with Sourcegraph
  chat [options]  Chat with codebase context.
  
  Examples:
    cody chat -m 'Tell me about React hooks'
    cody chat --context-file README.md --message 'Summarize this readme'
    git diff | cody chat --stdin -m 'Explain this diff'
  
  Enterprise Only:
    cody chat --context-repo github.com/sourcegraph/cody --message 'What is the agent?'
  models          Manage models
  api
  internal
  help [command]  display help for command

[kalanchan]

I'm not too familiar with how the CLI is built and released, @olafurpg would you know more?

[olafurpg]

The CLI is effectively distributed the same way as the JB plugin. Or put differently, the JB plugin effectively embeds Cody CLI.

It's a Node.js script with some required dependencies that we vendor with the npm package.

Any concrete question you had in mind?

[jdpleiness]

@Chickensoupwithrice Are the CI failures okay in this context or something that is failing with the image?

[DaedalusG]

Similar question about using wolfi, but not blocking

[Chickensoupwithrice]

The CI failures are totally unrelated to the image, I'm not sure why, but they seem to fail pretty consistently?

[Chickensoupwithrice]

Alright, it's built and running on Alpine :)