add more docs

Author: lrvideckis

library/data_structures_[l,r)/bit_uncommon/kd_bit.hpp

@@ -3,6 +3,8 @@
 //! @code
 //!   KD_BIT<2> bit(n, m);
 //!   bit.update(i, j, 5);
+//!   // 0 <= i < n
+//!   // 0 <= j < m
 //!   bit.query(i1, i2, j1, j2);
 //!   // 0 <= i1 <= i2 <= n
 //!   // 0 <= j1 <= j2 <= m