Add /shrug command

Certain popular web-based chat systems support a `/shrug` command which
appends the ¯\\_(ツ)_/¯ text emoticon (kaomoji) to a message. I've often
found myself wishing Riot had something similar, so I decided to add it
myself. (If Riot ever gets a user-extensible /-command system, this will
probably no longer be necessary. But since it doesn't have that, here I
am). Doesn't support markdown / rich text messages because I didn't want
to dig that far into Riot/the SDKs for my first PR; if someone else
would like to add that, by all means.

Signed-off-by: Andrew Chronister <chr@chronal.net>

src/SlashCommands.js

@@ -70,6 +70,19 @@ function success(promise) {
 /* eslint-disable babel/no-invalid-this */
 
 export const CommandMap = {
+    shrug: new Command({
+        name: 'shrug',
+        args: '<message>',
+        description: _td('Prepends ¯\\_(ツ)_/¯ to a plain-text message'),
+        runFn: function(roomId, args) {
+            var message = '¯\\_(ツ)_/¯'
+            if (args) {
+                message = message + ' ' + args
+            }
+            return success(MatrixClientPeg.get().sendTextMessage(roomId, message));
+        }
+    }),
+
     ddg: new Command({
         name: 'ddg',
         args: '<query>',