Add manual trigger to publish tweet

.github/workflows/publish_tweet.yml

@@ -1,6 +1,7 @@
 name: Publish tweet
 
 on:
+  workflow_dispatch:
   schedule:
     # <minute [0,59]> <hour [0,23]> <day of the month [1,31]> <month of the year [1,12]> <day of the week [0,6]>
     # https://pubs.opengroup.org/onlinepubs/9699919799/utilities/crontab.html#tag_20_25_07