Add [] as word boundaries

This is a common boundary used in markdown link text

src/packages/spell-check/lib/spell-check-handler.coffee

@@ -1,6 +1,6 @@
 module.exports =
   findMisspellings: (text) ->
-    wordRegex = /(?:^|\s)([a-zA-Z']+)(?=\s|\.|$)/g
+    wordRegex = /(?:^|[\s\[\]])([a-zA-Z']+)(?=[\s\.\[\]]|$)/g
     row = 0
     misspellings = []
     for line in text.split('\n')