Huddle landing page (mobile-first, sass, flexbox)

Hi,

to set the proper layout (split the page to the proper details/sass partials) to prevent to have the flexbox almost everywhere and have the overcomplicated solution was the most difficult for me in this challenge.

I have fixed some accesibility and HTML issues that were spotted.

Will be glad for any comments how the code or the solution could be better.

Thank you.