Add link to reference or tutorial in "Welcome" screen

[Potherca]

The "Welcome" screen on first load (before the first save has been created) should have a link to a reference or tutorial.

To take a new user by the hand, this could be part of an "Unsure what to build?" suggestion.

simplycode-docker/403.php

Lines 84 to 91 in cefb0d1

	<h1>Welcome to SimplyCode!</h1>
	<p>
	This looks like your first visit.
	<strong>Go to <a href="%s">%s</a> to start building something awesome.</strong>
	<!-- @TODO: Add a link to a turorial or reference to help the user
	See: https://github.com/SimplyEdit/simplycode-docker/issues/12
	-->
	</p>

[Hoxolotl]

Made a branch, added link and explanation
waiting for merge.

[Potherca]

Branch reviewed, waiting for change.

[Hoxolotl]

Change made