CSHShydRology 1.6

replaces Travis with GitHub Actions. Travis shut down travis-ci.org and moved open-source projects onto a credit-based pla.
checks the package on every push to master and every pull request on five configurations: macOS and Windows on the current R release, plus R devel, release and old-release on Linux.

CSHShydRology 1.5.1

the packages ggspatial, httr2, terra, tidyhydat, tidyterra and whitebox have been moved from Imports to Suggests, as they are frequent sources of CRAN check failures. Functions that need one of these packages now check for it and stop with an informative message if it is not installed, so the rest of the package remains usable without them.
calls to the above packages are now fully qualified (pkg::function()) and their importFrom directives have been removed, as a package in Suggests cannot be imported in NAMESPACE
examples that require one of these packages, an external executable or a download are now wrapped in \dontrun{}

functions from the packages terra and tidyterra have replaced raster, which is deprecated, in the catchment delineation functions

changes to hydrograph plotting functions, including adding ch_gg_hydrographs which creates ggplot2 objects
removal of function ch_flow_raster_trend as it used the package Kendal, which will be archived by CRAN

added functions ch_high_Grubbs_test and ch_ffa_screen_plot to identify outliers when fitting distributions to mean daily streamflows
updated urls to specify https instead of http

minor fixes to return statements in ch_tr_sign and ch_tr_signif
fixed some URLs which redirect to other locations
removed functions ch_get_map_base and ch_map_plot_data as we could not trap the error resulting from accessing the server. We hope to be able to restore these functions in the future.

revised examples of functions using tidyhydat to use small test database to avoid issues with CRAN testing

changed several flags to to prevent errors when running check --as-cran --run-donttest

all function examples using Whitebox now test for the presence of the Whitebox executable before running
- this avoids the Whitebox functions returning an error when tested if there is no executable installed
- allows us to remove the flag from several functions

fixed many issues causing problems with check --as-cran
functions now fail gracefully attempting to download data if url is incorrect or file is missing
improved package Description