Removal of array constructor ".last()" so that this project does not clash with other custom array methods

[egilll]

Removal of array constructor ".last()" so that this project does not clash with other custom array methods.

Some other packages, like array-sugar, add new methods for arrays.

When such packages are used with html2json, HTML parsing will fail because of the clash of the newly created array methods ".last" and ".last()".

The proposed change removes the custom array method and uses vanilla Javascript instead.

The error that will otherwise pop up is: stack.last is not a function.