gander 0.1.0

• Initial CRAN submission.

Notable changes pre-CRAN submission

Early adopters of the package will note two changes made shortly before the
release of the package to CRAN:

• The configuration options .gander_fn and .gander_args have been
  transitioned to one option, .gander_chat. That option takes an ellmer Chat, e.g.
  options(.gander_chat = ellmer::chat_claude()).
  If you've configured an ellmer model using the previous options, you'll get
  an error that automatically translates to the new code you need to use.

• There is no longer a default ellmer model. Early in the development
  of gander, if you had an ANTHROPIC_API_KEY set up, the addin would
  "just work." While this was convenient for Claude users, it means that the
  package spends money on the users behalf without any explicit opt-in.