Add option to send/edit a message with Ctrl + Enter / Command + Enter

When editing multi-line text this option helps to prevent accidentally
sending a message too early. With this option, Enter just inserts a new
line.

For example, composing programming code in a dev chat becomes much
easier when Enter just inserts a new line instead of sending the
message.

Signed-off-by: Clemens Zeidler <clemens.zeidler@gmail.com>

src/settings/Settings.ts

@@ -321,6 +321,11 @@ export const SETTINGS: {[setting: string]: ISetting} = {
         displayName: _td("Show typing notifications"),
         default: true,
     },
+    "MessageComposerInput.ctrlEnterToSend": {
+        supportedLevels: LEVELS_ACCOUNT_SETTINGS,
+        displayName: _td("Use Ctrl + Enter to send a message (Mac: Command + Enter)"),
+        default: false,
+    },
     "MessageComposerInput.autoReplaceEmoji": {
         supportedLevels: LEVELS_ACCOUNT_SETTINGS,
         displayName: _td('Automatically replace plain text Emoji'),