History of decodeURIComponent()

note that it can throw an exception – bug 1303936

Adjust wording of Return value

Adjust wording of Return value (consistent with other unescape methods)

Add "Return value" section as per Bug 1287421

add ES draft

change "method" to "function" (for consistency)

fix compat parsing error; cleanup

Even if the "decodeURI" function could be used, i think that "decodeURIComponent" is more appropriate in this article.