add comment about complex regex in pagination

app/assets/javascripts/vue_pagination/index.js.es6

@@ -27,6 +27,8 @@
         const { totalPages, nextPage, previousPage } = this.pageInfo;
 
         if (text === SPREAD) return;
+        // the regex here is to read if the string coming in will become a valid string
+        // had issues with parsing using `+` because `typeof NaN === 'number'`
         if (/^-?[\d.]+(?:e-?\d+)?$/.test(text)) pagenum = +text;
         if (text === LAST) pagenum = totalPages;
         if (text === NEXT) pagenum = nextPage;