Add support for BigInt ranges

[JeffFessler]

Addresses #37

Dims is hardwired to a type of Int which is too restrictive for BigInt ranges,
so this PR replaces Dims with NTuple{D,Integer}

It is unknown whether this generalization would slow things down, so I might not merge until someone actually requests this change.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (6440098) to head (baa256c).

Additional details and impacted files

@@            Coverage Diff            @@
##              main       #39   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            8         8           
  Lines           59        60    +1     
=========================================
+ Hits            59        60    +1     

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[JeffFessler]

This would require a version bump because of the type changes.