readme operator[] typo (#2)

Author: jpreiss

README.md

@@ -3,7 +3,7 @@ A simple c++17 header only library that implements structure of arrays data stru
 These are the most useful operations.  
 - `.insert(field1, field2, ...)` field_n inserts into the nth array
 - `.sort_by_field<col_idx>()` sort all columns in tandem based on particular column 
-- `.operator()[row_idx]` read data out as tuple of references
+- `.operator[](row_idx)` read data out as tuple of references
 - `.get_column<col_idx>()` direct access to underlying std::vector column
 - `.view<col_idx1, col_idx2, ...>(row_idx)` read subset of the fields out as a tuple of references