docs: coder-server does not support offline mode

[Michael Brewer]

code-server docs mentions an offline mode, but this has not been implemented

module "code-server" {
  source         = "registry.coder.com/modules/code-server/coder"
  version        = "1.0.7"
  agent_id       = coder_agent.main.id
  folder         = "/workspace/${local.folder_name}"
  install_prefix = "/workspace/.coder-server"
  offline = true
  settings = {
    "workbench.colorTheme" : "Visual Studio Dark"
    "workbench.startupEditor" : "readme"
  }
  extensions = [
    "ms-python.python",
    "hashicorp.terraform",
    "ms-azuretools.vscode-docker"
  ]
}

However there is no filed for this

Error: Unsupported argument
on main.tf line 219, in module "code-server":
  219:   offline = true
An argument named "offline" is not expected here.

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Of coz having offline mode support by this module would be ideal