docs(Dropdown): add DropdownSearchInput example

docs/app/Examples/modules/Dropdown/Usage/DropdownExampleSearchInput.js

@@ -0,0 +1,21 @@
+import React from 'react'
+import { Dropdown } from 'semantic-ui-react'
+
+const options = [
+  { key: '100', text: '100', value: 100 },
+  { key: '200', text: '200', value: 300 },
+  { key: '300', text: '300', value: 300 },
+  { key: '400', text: '400', value: 400 },
+]
+
+const DropdownExampleSearchInput = () => (
+  <Dropdown
+    search
+    searchInput={{ type: 'number' }}
+    selection
+    options={options}
+    placeholder='Select amount...'
+  />
+)
+
+export default DropdownExampleSearchInput

docs/app/Examples/modules/Dropdown/Usage/index.js

@@ -76,6 +76,11 @@ const DropdownUsageExamples = () => (
       description='A dropdown item can be rendered differently inside the menu.'
       examplePath='modules/Dropdown/Usage/DropdownExampleItemContent'
     />
+    <ComponentExample
+      title='Search Input'
+      description='A dropdown implements a search input shorthand.'
+      examplePath='modules/Dropdown/Usage/DropdownExampleSearchInput'
+    />
     <ComponentExample
       title='Upward'
       description='A dropdown can open its menu upward.'