Random access range that iterates over the string by bytes, in forward order.
auto s = String("Plutarchus"); auto r = s[]; assert(r.front == 'P'); assert(r.back == 's'); r.popFront(); assert(r.front == 'l'); assert(r.back == 's'); r.popBack(); assert(r.front == 'l'); assert(r.back == 'u'); assert(r.length == 8);
auto s = const String("Was ich vermag, soll gern geschehen. Goethe"); auto r1 = s[]; assert(r1.front == 'W'); auto r2 = r1[]; r1.popFront(); assert(r1.front == 'a'); assert(r2.front == 'W');