add key shortcut for submitting from compose

this adds an event listener on the text area of the composer
it listens for a keydown event with both <enter> and either <control> on
windows and linux or <command> on osx then it fires the locally scoped
method 'publish' and prevents default event handling

Author: robjloranger

modules/message/html/compose.js

@@ -59,6 +59,12 @@ exports.create = function (api) {
         if (!files || !files.length) return
         attachFiles(files)
       },
+      'ev-keydown': ev => {
+        if (ev.key === 'Enter' && (ev.ctrlKey || ev.metaKey)) {
+          publish()
+          ev.preventDefault()
+        }
+      },
       disabled: publishing,
       placeholder
     })