Add Lesson Container #18

[Pliavi]

Add #18

• Add LessonButtonCollab to components
• Add LessonsCollab to containers
• Add scrollbar CSS to generics
• Add --color-granite-grey color to settings/color

I have some to ask, what will come from a lesson?
I made the list based in a counter, as the lesson button is nothing than a button with a numbered link, with any meta or information, so i'm generating a list with just numbers to simulate a for-loop (and svelte doesn't have it)

I had done the list to scroll to the active lesson, but when I created a new component to the LessonButton the bind:this stopped referencing the RealDOM to reference the own dev-component, so I had to remove it, may it can be got using the HTML id attribute and the url hash.