FEATURE: allow blocking emojis (#7011)

https://meta.discourse.org/t/blocking-emojis-wont-work/105853

app/services/word_watcher.rb

@@ -19,7 +19,7 @@ class WordWatcher
         nil
       else
         regexp = '(' + words.map { |w| word_to_regexp(w) }.join('|'.freeze) + ')'
-        SiteSetting.watched_words_regular_expressions? ? regexp : "\\b(#{regexp})\\b"
+        SiteSetting.watched_words_regular_expressions? ? regexp : "(?<!\\w)(#{regexp})(?!\\w)"
       end
     end
     s.present? ? Regexp.new(s, Regexp::IGNORECASE) : nil