Amend the Trigger to parse options and switches

• -arg=value sets arg to value
• -arg sets arg to true
• -arg! sets arg to false

Options must be placed at the start of the arguments (directly after the trigger), as soon an argument starts without a dash, options parsing stops.

The prefix sign is - but for "compatibility" we will also match "--" and iOS safe "—".

!trigger -format=md arg1 arg2 arg3
# => %{options: %{"format" => "md", args: ["arg1", ...]}

!trigger -hello world -deep deep
# => %{options: %{"hello" => true, args: ["world", "-deep", ...]}

As the options is very plugin-specific and may eat text and break behavior, Options expansion should be performed before delivering the option to the plugin. The plugin should disclose the options it can when subscribing

{:ok, _} = Registry.register(IRC.PubSub, "trigger:something", [plugin: __MODULE__,
  trigger_options: %{
    :opt1 => %{type: "string", default: nil},
    :opt2 => %{type: "boolean", default: true},
    …
  }
)

Expansion should also be performed manually by calling IRC.Trigger.expand_options(trigger, options_schema).