move assets, styles to docs folder

mkdocs/styles/extra.css

@@ -1,10 +0,0 @@
-@import url('https://fonts.googleapis.com/css2?family=Nunito+Sans:ital,opsz,wght@0,6..12,200..1000;1,6..12,200..1000&display=swap');
-@import url('https://fonts.googleapis.com/css2?family=Merriweather:ital,opsz,wght@0,18..144,300..900;1,18..144,300..900&display=swap');
-
-:root {
-  --md-text-font: "Merriweather"
-}
-
-.md-nav__title {
-  font-family: "Nunito Sans";
-}