Created footer, fixed header, created 404, main page, base for pages

src/components/App.js

src/components/Footer.js

src/components/Header.js

src/components/Main.js

src/components/images/kszk_big_logo.png

src/components/images/kszk_logo.svg

src/components/pages/Circles.js

src/components/pages/Home.js

src/components/pages/NotFound.js

src/components/pages/Profile.js

src/components/pages/Schedule.js

src/components/pages/Statistics.js

src/components/pages/Trainers.js