Fix issues from CRAN manual inspection

[RasmusSkytte]

Intent

The CRAN submission process highlighted a few minor issues. These are fixed here.

Approach

• Some formatting changes

• tempdir() used to write files rather than package folder (still optionally available)

• \dontrun in %.% example replaced with commented-out code

Known issues

N/A

Checklist

• The PR passes all local unit tests
• I have documented any new features introduced
• If the PR adds a new feature, please add an entry in NEWS.md
• A reviewer is assigned to this PR

[RasmusSkytte]

Like with #93, the changes in this PR are so minor they do not merit a PR.
I created this PR to get the testing feedback from our CI tests so that I can submit to CRAN.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (3c5a86f) 96.77% compared to head (36de3b9) 96.77%.
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #95   +/-   ##
=======================================
  Coverage   96.77%   96.77%           
=======================================
  Files          12       12           
  Lines         590      590           
=======================================
  Hits          571      571           
  Misses         19       19           

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