This How-To is for adding fonts to the Redactor plugin "fontfamily" in a package. The original fontfamily plugin just adds a dropdown with a few fonts.
In 5.6, we could use $_SESSION but in 5.7, there is a built-in session class from Symphony.
Use Composer to declare your dependencies and download a third party library for use in your package. This example will use Stripe PHP.
In 5.6 we always had the possibility to override any class in the core. How can we do this in 5.7?
Although concrete5 features an auto-updater, there is also the option to manually upgrade a site to a new version through some simple steps. The video in this how-to demonstrates how to perform a manual upgrade on a typical server.
How to create modal dialogs on dashboard single pages in packages.
How to add a menu item (when viewing a page)
How to use the form widget and new input types available in 5.7. A working Form Widget Examples block is included with this How-To.