Update interpolation_cross.rst

line 20 : Now run the *Shapes to grid* to ----> the word 'algorithm' is missing after 'the'

line 24 : At this points, we know ----> 'points' should be singular 'point' 

line 24 : We can compare the by computing the ----> the word 'two', which refers to the two layers to compare, is missing after 'the'
Merge pull request #428 from DiGro/patch-1

Update interpolation_cross.rst