Implement hotkeys for web UI (#5164)

* Fix #2102 - Implement hotkeys

Hotkeys on status list:

- r to reply
- m to mention author
- f to favourite
- b to boost
- enter to open status
- p to open author's profile
- up or k to move up in the list
- down or j to move down in the list
- 1-9 to focus a status in one of the columns
- n to focus the compose textarea
- alt+n to start a brand new toot
- backspace to navigate back

* Add navigational hotkeys

The key g followed by:

- s: start
- h: home
- n: notifications
- l: local timeline
- t: federated timeline
- f: favourites
- u: own profile
- p: pinned toots
- b: blocked users
- m: muted users

* Add hotkey for focusing search, make escape un-focus compose/search

* Fix focusing notifications column, fix hotkeys in compose textarea

app/javascript/mastodon/components/autosuggest_textarea.js

@@ -125,6 +125,16 @@ export default class AutosuggestTextarea extends ImmutablePureComponent {
     this.props.onKeyDown(e);
   }
 
+  onKeyUp = e => {
+    if (e.key === 'Escape' && this.state.suggestionsHidden) {
+      document.querySelector('.ui').parentElement.focus();
+    }
+
+    if (this.props.onKeyUp) {
+      this.props.onKeyUp(e);
+    }
+  }
+
   onBlur = () => {
     this.setState({ suggestionsHidden: true });
   }
@@ -173,7 +183,7 @@ export default class AutosuggestTextarea extends ImmutablePureComponent {
   }
 
   render () {
-    const { value, suggestions, disabled, placeholder, onKeyUp, autoFocus } = this.props;
+    const { value, suggestions, disabled, placeholder, autoFocus } = this.props;
     const { suggestionsHidden } = this.state;
     const style = { direction: 'ltr' };
 
@@ -195,7 +205,7 @@ export default class AutosuggestTextarea extends ImmutablePureComponent {
             value={value}
             onChange={this.onChange}
             onKeyDown={this.onKeyDown}
-            onKeyUp={onKeyUp}
+            onKeyUp={this.onKeyUp}
             onBlur={this.onBlur}
             onPaste={this.onPaste}
             style={style}