lightr 1.8.0

Minor changes

• timezones for converted OceanOptics files are now handled differently internally (@Bisaloo, #64),
  to handle changes in upstream tzdata 2024b, which removed for example the CET and EST timezone codes.
  This may result in some other deprecated timezone codes not being handled correctly.
  Please report any bugs or discrepancies you may notice in the datetime field of metadata.
• lightr now depends on R >= 4.0.0, following the tidyverse recommendation (@Bisaloo, #28)
• the future package is now explicitly listed as a dependency, removing an R CMD check NOTE and thus removing the strain on CRAN reviewers (@Bisaloo, #63).
  The future package was already a indirect dependency via the future.apply package.