feat(option): add support for functional option arguments

[ardnew]

This adds support for the so-called "Functional Options" pattern to configure menu.Model.

This pattern makes it much easier to add optional configurations without breaking any existing code or external interfaces.

In particular, a handful of Option functions have been added for more control over the embedded list.Model.

[ardnew]

This PR adds support to menu.Model for the following features by providing indirect access to the underlying list.Model (from package github.com/charmbracelet/bubbles/list):

• Show list page indicator
  • WithShowPagination(bool) Option
• Show list title
  • WithShowTitle(bool) Option
• Enable support for filtering list items interactively
  • WithFilteringEnabled(bool) Option
• Show active filter status
  • WithShowFilter(bool) Option
• Show list status (item count)
  • WithShowStatusBar(bool) Option
• Show available keybindings (supports toggling short-help and full-help)
  • WithShowHelp(bool) Option
• Define keybindings and descriptions shown in full-help
  • WithAdditionalFullHelpKeys(func([]key.Binding) []key.Binding) Option
• Define keybindings and descriptions shown in short-help
  • WithAdditionalShortHelpKeys(func([]key.Binding) []key.Binding) Option

These options are intended to be used as lambda functions/closures passed as arguments with the variable-length parameter list of the package's primary constructor New(string, []Choice, *Choice, ...Option) Model