Add a redundancy column to rs.algorithms.merge() output about reciprocalspaceship HOT 1 CLOSED

> mtz = rs.read_mtz("docs/examples/data/HEWL_unmerged.mtz")
> mtz.head()
       BATCH         I      SIGI  PARTIAL
H K L                                    
0 0 4    137  696.5212  87.83294    False
    4    520  710.6812 88.107025    False
    4    856 672.05634  87.75671    False
    4   1239 642.47485  87.90302    False
    4   2160 655.71783  87.74394    False
> rs.algorithms.merge(mtz)
             IMEAN   SIGIMEAN      I(+)    SIGI(+)      I(-)    SIGI(-)  N(+)  N(-)
H  K  L                                                                            
0  0  4  661.29987  21.953098 661.29987  21.953098 661.29987  21.953098    16    16
      8  3229.6492 105.980934 3229.6492 105.980934 3229.6492 105.980934    16    16
      12 1361.8672   43.06085 1361.8672   43.06085 1361.8672   43.06085    16    16
      16  4124.393  196.89108  4124.393  196.89108  4124.393  196.89108     8     8
1  0  1   559.3369   8.626299  559.3369   8.626299  559.3369   8.626299    64    64
...            ...        ...       ...        ...       ...        ...   ...   ...
14 11 20   35.6825   8.251703       NaN        NaN   35.6825   8.251703     0     2
   10 20 52.386147  10.075351       NaN        NaN 52.386147  10.075351     0     2
   9  20 122.96966  13.823673       NaN        NaN 122.96966  13.823673     0     3
   8  20 149.46716  13.995815       NaN        NaN 149.46716  13.995815     0     4
11 7  20 25.917196   8.322451       NaN        NaN 25.917196   8.322451     0     2

[12542 rows x 8 columns]