Update 03_A_First_Static_Page.md

Does not build with react.css.css for me (reported in kotlin-hands-on/web-app-react-kotlin-js-gradle#22)

Author: beshur

Building Web Applications with React and Kotlin JS/03_A_First_Static_Page.md

@@ -7,7 +7,7 @@ Replace the code inside `src/main/kotlin/Main.kt` with the following:
 ```kotlin
 import kotlinx.browser.document
 import react.*
-import react.css.css
+import emotion.css.css
 import react.dom.render
 import csstype.Position
 import csstype.px