[Beta] useContext API (#4378)

* [Beta] useContext API

* Simplify + add

* Tweaks

* Softer

* Tweaks

* Small tweaks

beta/src/pages/apis/useref.md

@@ -15,6 +15,7 @@ const ref = useRef(initialValue)
 - [Usage](#usage)
   - [Referencing a value with a ref](#referencing-a-value-with-a-ref)
   - [Manipulating the DOM with a ref](#manipulating-the-dom-with-a-ref)
+  - [Exposing a ref from your component](#exposing-a-ref-from-your-component)
   - [Avoiding recreating the ref contents](#avoiding-recreating-the-ref-contents)
 - [Reference](#reference)
   - [`useRef(initialValue)`](#useref)

beta/src/sidebarReference.json

@@ -15,6 +15,10 @@
               "title": "useState()",
               "path": "/apis/usestate"
             },
+            {
+              "title": "useContext()",
+              "path": "/apis/usecontext"
+            },
             {
               "title": "useRef()",
               "path": "/apis/useref"