Update lexer for the Chapel programming language (#1423)
Update lexer for the Chapel programming language (#1423)

* Add the import keyword to the list of keywords

* Update the website link at the top of the class

While the old link still redirects to the new one, it's better to just have the
new link (we've been using this link for a few years now so it's not actually
that new, but still).
pygments/pygments,pygments/pygments,pygments/pygments,pygments/pygments,dscorbett/pygments,pygments/pygments,pygments/pygments,pygments/pygments,pygments/pygments,dscorbett/pygments,dscorbett/pygments,dscorbett/pygments,dscorbett/pygments,dscorbett/pygments,pygments/pygments,dscorbett/pygments,pygments/pygments,pygments/pygments,dscorbett/pygments,dscorbett/pygments,dscorbett/pygments,dscorbett/pygments,pygments/pygments,dscorbett/pygments,dscorbett/pygments,pygments/pygments,pygments/pygments,dscorbett/pygments,pygments/pygments,pygments/pygments,dscorbett/pygments,dscorbett/pygments,dscorbett/pygments,pygments/pygments,dscorbett/pygments,pygments/pygments