DOC: Add array representations to sparse array construction examples

[alugowski]

Reran the examples in Construct Sparse Arrays with matrepr installed to show the result of each snippet.

Previously only the first example showed the result, but only as a dense array. This change illustrates the sparsity of the sparse arrays. Some examples become easier to follow, such as the last example showing a "bad" identity matrix with explicit zeros and a fill value of 1. A visualization of the array reinforces the written description.

[alugowski]

The pre-commit.ci test fails with this message:

=====> .pre-commit-config.yaml is not a file

that all recent PRs appear to encounter.

[codecov]

Codecov Report

Merging #606 (20bc176) into master (790f6d5) will not change coverage.
The diff coverage is n/a.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #606   +/-   ##
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  Coverage   90.43%   90.43%           
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  Files          20       20           
  Lines        3564     3564           
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  Hits         3223     3223           
  Misses        341      341           

[hameerabbasi]

@alugowski This seems to need a rebase after #616 and #617. CI is also green again.

[alugowski]

@alugowski This seems to need a rebase after #616 and #617. CI is also green again.

Done!

[hameerabbasi]

Thanks for your contribution, @alugowski