Issue931 onset-to-onset timewindow

[jhmigueles]

Closes #931 => Allow for the calculation of sleep onset to sleep onset windows ("OO") in part 5.

Checklist before merging:

• Existing tests still work (check by running the test suite, e.g. from RStudio).
• Added tests (if you added functionality) or fixed existing test (if you fixed a bug).
• Updated or expanded the documentation.
• Updated release notes in inst/NEWS.Rd with a user-readable summary. Please, include references to relevant issues or PR discussions.
• Added your name to the contributors lists in the DESCRIPTION and CITATION.cff files.

[codecov-commenter]

Codecov Report

Merging #933 (050d549) into master (0e67881) will increase coverage by 0.03%.
The diff coverage is 90.90%.

❗ Current head 050d549 differs from pull request most recent head 0069997. Consider uploading reports for the commit 0069997 to get more accurate results

❗ Your organization needs to install the Codecov GitHub app to enable full functionality.

@@            Coverage Diff             @@
##           master     #933      +/-   ##
==========================================
+ Coverage   78.18%   78.21%   +0.03%     
==========================================
  Files          93       93              
  Lines       12334    12352      +18     
==========================================
+ Hits         9643     9661      +18     
  Misses       2691     2691              

Files	Coverage Δ
R/g.part5.R	79.92% <100.00%> (+0.28%)	⬆️
R/g.part5.definedays.R	82.05% <100.00%> (+1.86%)	⬆️
R/g.report.part5.R	85.24% <50.00%> (ø)