this is some initial plumbing bits around configuration before we get into interacting with the api.

• adds a config package that manages env vars/api keys.
• loops login will store the api key in keychain (macOS) or other pass keepers on different platforms. once ive wired up the api-key endpoint, we'll validate the key is valid before saving it.
• loops logout will remove stored credentials.
• LOOPS_API_KEY takes precedence over a stored key.
• LOOPS_ENDPOINT_URL is only available in the env and used to override the prod api endpoint for testing purposes.
• adds a temporary debug command to print the config setting that were selected.

login/out,

➜ task -- login
task: [default] go run ./... login
Enter your API key:
API key saved.

➜ task -- logout
task: [default] go run ./... logout
Logged out.

debug,

➜ task -- debug
task: [default] go run ./... debug
{
  "APIKey": "asdf",
  "EndpointURL": "https://app.loops.so/api/v1"
}

➜ LOOPS_ENDPOINT_URL=https://example.com LOOPS_API_KEY=ok task -- debug
task: [default] go run ./... debug
{
  "APIKey": "ok",
  "EndpointURL": "https://example.com"
}