Adding API descriptions

src/pages/reference/index.md

@@ -1,6 +1,7 @@
 ---
 title: React APIs
 layout: API
+description: "Hooks, ReactDOM, and more APIs."
 ---
 
 <Intro>

src/pages/reference/reactdom.md

@@ -1,6 +1,7 @@
 ---
 title: ReactDOM API
 layout: API
+description: "ReactDOM lets you render React components on a webpage."
 ---
 
 <Intro>

src/pages/reference/render.md

@@ -1,6 +1,7 @@
 ---
 title: render()
 layout: API
+description: "Renders a piece of JSX into a browser DOM container node."
 ---
 
 <Intro>

src/pages/reference/usestate.md

@@ -1,6 +1,7 @@
 ---
 title: useState()
 layout: API
+description: "useState is a Hook for 'remembering' information between renders and triggering renders."
 ---
 
 <Intro>