add CSS resources (#946)

* add react.js resources

* add css resources

content/roadmaps/100-frontend/content/102-css/readme.md

@@ -1 +1,8 @@
-# Css
+# CSS
+
+Cascading Style Sheets (CSS) is a simple mechanism for adding style (e.g., fonts, colors, spacing) to Web documents.
+
+<ResourceGroupTitle>Free Content</ResourceGroupTitle>
+<BadgeLink badgeText='Read' colorScheme='yellow' href='https://www.w3schools.com/css/'>CSS Tutorial by W3Schools</BadgeLink>
+<BadgeLink badgeText='Read' colorScheme='yellow' href='https://learn.shayhowe.com/html-css/'>Learn to Code HTML & CSS by Shay Howe</BadgeLink>
+<BadgeLink badgeText='Course' colorScheme='green' href='https://www.freecodecamp.org/learn/responsive-web-design/'>freeCodeCamp Responsive Web Design Course</BadgeLink>