Sets boolean to allow user input. The default behaviour of Vedeu is to be interactive. This is the same as setting Vedeu::Config::API#standalone to false.

# Set:
# same as `interactive true` or `standalone false`.
Vedeu.configure do
  interactive!
  # ...
end

# => Allow user input.
Vedeu.configure do
  interactive true
  # ...
end

# => Disallow user input.
Vedeu.configure do
  interactive false
  # ...
end

# Get:
Vedeu.config.interactive?
Vedeu.config.interactive