Support "row vectors" and simplify positional argument defaults

[JeffFessler]

Also support N x 1 arrays.

Also switches to using Requires as suggested in #5

[codecov]

Codecov Report

Merging #6 (765d95f) into main (eb2112c) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##              main        #6   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            1         2    +1     
  Lines           12        13    +1     
=========================================
+ Hits            12        13    +1     

Impacted Files	Coverage Δ
src/Sound.jl	100.00% <100.00%> (ø)
src/sample-buf.jl	100.00% <100.00%> (ø)

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