Add new defcustom js-jsx-align->-with-<

Add new defcustom js-jsx-align->-with-<

* lisp/progmodes/js.el (js-jsx-align->-with-<): New variable for users
to control one opinionated aspect of JSX indentation.  It defaults to
the style seen in the React docs, which many users expected as the
“correct” indentation.  Still, the old SGML-style of indentation could
be desirable too, especially since it was the old default.  This
ensures users have a way of getting back the old behavior.
(js-jsx--contextual-indentation): Respect js-jsx-align->-with-<.

* test/manual/indent/jsx-align-gt-with-lt.jsx: New test for
js-jsx-align->-with-<.