docs(Portal): add Example under Addons Section of Docs (#1860)

* initial commit

* fixes linitng erros

* chore(permissions): restore to 0644

* chore(permissions): restore to 0755

* style(Portal): cleanup example

docs/app/Examples/addons/Portal/Types/PortalExamplePortal.js

@@ -0,0 +1,58 @@
+import React, { Component } from 'react'
+import { Button, Grid, Header, Segment, Portal } from 'semantic-ui-react'
+
+export default class ExamplePortal extends Component {
+  state = {
+    log: [],
+    open: false,
+  }
+
+  handleOpen = () => {
+    this.setState({ open: true })
+    this.writeLog('Portal mounted')
+  }
+
+  handleClose = () => {
+    this.setState({ open: false })
+    this.writeLog('Portal closed')
+  }
+
+  writeLog = message => this.setState({ log: [message, ...this.state.log] })
+
+  render() {
+    const { log, open } = this.state
+
+    return (
+      <Grid columns={2}>
+        <Grid.Column>
+          <Portal
+            closeOnTriggerClick
+            openOnTriggerClick
+            trigger={(
+              <Button
+                content={open ? 'Close Portal' : 'Open Portal'}
+                negative={open}
+                positive={!open}
+              />
+            )}
+            onOpen={this.handleOpen}
+            onClose={this.handleClose}
+          >
+            <Segment style={{ left: '40%', position: 'fixed', top: '50%', zIndex: 1000 }}>
+              <Header>This is an example portal</Header>
+              <p>Portals have tons of great callback functions to hook into.</p>
+              <p>To close, simply click the close button or click away</p>
+            </Segment>
+          </Portal>
+        </Grid.Column>
+        <Grid.Column>
+          <Segment>
+              <pre style={{ height: 200, overflowY: 'scroll' }}>
+                {log.map((e, i) => <p key={i}>{e}</p>)}
+              </pre>
+          </Segment>
+        </Grid.Column>
+      </Grid>
+    )
+  }
+}

docs/app/Examples/addons/Portal/Types/index.js

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+import React from 'react'
+
+import ComponentExample from 'docs/app/Components/ComponentDoc/ComponentExample'
+import ExampleSection from 'docs/app/Components/ComponentDoc/ExampleSection'
+
+const PortalTypesExamples = () => (
+  <ExampleSection title='Types'>
+    <ComponentExample
+      title='Portal'
+      description='A basic portal.'
+      examplePath='addons/Portal/Types/PortalExamplePortal'
+    />
+  </ExampleSection>
+)
+
+export default PortalTypesExamples

docs/app/Examples/addons/Portal/index.js

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+import React from 'react'
+import Types from './Types'
+
+const PortalExamples = () => (
+  <div>
+    <Types />
+  </div>
+)
+
+export default PortalExamples