Handle alt+enter in the spoiler input as shortcut for secondary post

Fixes #780

app/javascript/flavours/glitch/features/composer/index.js

@@ -437,6 +437,7 @@ class Composer extends React.Component {
           intl={intl}
           onChange={handleChangeSpoiler}
           onSubmit={handleSubmit}
+          onSecondarySubmit={handleSecondarySubmit}
           text={spoilerText}
           ref={handleRefSpoilerText}
         />

app/javascript/flavours/glitch/features/composer/spoiler/index.js

@@ -25,13 +25,19 @@ const handlers = {
     ctrlKey,
     keyCode,
     metaKey,
+    altKey,
   }) {
-    const { onSubmit } = this.props;
+    const { onSubmit, onSecondarySubmit } = this.props;
 
     //  We submit the status on control/meta + enter.
     if (onSubmit && keyCode === 13 && (ctrlKey || metaKey)) {
       onSubmit();
     }
+
+    // Submit the status with secondary visibility on alt + enter.
+    if (onSecondarySubmit && keyCode === 13 && altKey) {
+      onSecondarySubmit();
+    }
   },
 
   handleRefSpoilerText (spoilerText) {
@@ -87,5 +93,6 @@ ComposerSpoiler.propTypes = {
   intl: PropTypes.object.isRequired,
   onChange: PropTypes.func,
   onSubmit: PropTypes.func,
+  onSecondarySubmit: PropTypes.func,
   text: PropTypes.string,
 };