Support preserving location metadata of numbers, strings, etc.

[borkdude]

This is implemented as follows (excerpt from the README):

Postprocess read values:

(defrecord Wrapper [obj loc])

(defn iobj? [x]
  #?(:clj (instance? clojure.lang.IObj x)
     :cljs (satisfies? IWithMeta x)))

(parse-string "[1]" {:postprocess
                       (fn [{:keys [:obj :loc]}]
                         (if (iobj? obj)
                           (vary-meta obj merge loc)
                           (->Wrapper obj loc)))})

[#user.Wrapper{:obj 1, :loc {:row 1, :col 2, :end-row 1, :end-col 3}}]

This allows you to preserve metadata for objects that do not support carrying
metadata. When you use a :postprocess function, it is your responsibility to
attach location metadata.