When the plugin is activated, add a settings option

[emilse-webdev]

As I activate the plugin, I notice that there's a kind of "nothing changed" feeling, it takes me to come back again to the plugins page to see if it was activated, as I don't see any option nor in admin's menu, nor in tools, nor in settings, it generates the question "and if I want to create a shortcode now how?". I know it's on widgets page, but widgets depend on the theme, and the plugin would be good if it's independent, a page for adding the theme / plugin info and a shortcode is generated and can be copied is good.