public static Reader<String> attr(final String name) {
		return new AttrReader(name);
	}
Return a {@code Reader} for reading an attribute of an element.
<p>
<b>XML</b>
<pre> {@code <element length="3"/>}

<b>Reader definition</b>
{@snippet lang="java":
final Reader<Integer> reader =
    elem(
        v -> (Integer)v[0],
        "element",
        attr("length").map(Integer::parseInt)
    );
} </pre>

@param name the attribute name
@return an attribute reader
@throws NullPointerException if the given {@code name} is {@code null}
jenetics.xml/src/main/java/io/jenetics/xml/stream/Reader.java