Issue53 replace gdata

[vincentvanhees]

Fixes #53

Additionally, I added some importFrom declarations.

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 file.

[codecov-commenter]

Codecov Report

Attention: 13 lines in your changes are missing coverage. Please review.

Comparison is base (0694fd1) 0.00% compared to head (f9f9115) 0.00%.

❗ Current head f9f9115 differs from pull request most recent head ae4c22c. Consider uploading reports for the commit ae4c22c to get more accurate results

Files	Patch %	Lines
R/getwindows.R	0.00%	11 Missing ⚠️
R/frequency_domain_functions.R	0.00%	2 Missing ⚠️

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

Additional details and impacted files

@@          Coverage Diff          @@
##            main     #54   +/-   ##
=====================================
  Coverage   0.00%   0.00%           
=====================================
  Files          9       9           
  Lines        731     739    +8     
=====================================
- Misses       731     739    +8     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.