linkButton: refactor using React Hooks

src/web/util/linkButton.coffee

@@ -1,23 +1,17 @@
-import React from "react"
+import React, { useState } from "react"
 import { Redirect } from "react-router-dom"
 
 # A replacement of react Link that uses a button
-class LinkButton extends React.Component
-  constructor: (props) ->
-    super props
-    @state =
-      switch: false
+export default LinkButton = (props) ->
+  [jump, setJump] = useState false
 
-  render: ->
-    # We cannot just replace the button with a <Redirect/> when we switch
-    # because it will cause visual breaks where the button disappears for
-    # a short while before the actual switch happens.
-    <React.Fragment>
-      <button {...@props} onClick={(e) => @setState { switch: true }}/>
-      {
-        @state.switch and
-          <Redirect {...@props} />
-      }
-    </React.Fragment>
-
-export default LinkButton
+  # We cannot just replace the button with a <Redirect/> when we switch
+  # because it will cause visual breaks where the button disappears for
+  # a short while before the actual switch happens.
+  <React.Fragment>
+    <button {...props} onClick={(e) => setJump true}/>
+    {
+      jump and
+        <Redirect {...props} />
+    }
+  </React.Fragment>