Uses requireNamespace() to check if a package is already installed and
provides options for issuing an error, warning, etc. in case the package is
not installed.
Usage
check_for_pkg(package, func = stop)
Arguments
package
the name of the package to check for
func
what should this check call if the package is not installed?
This can be any function, but stop, warning, skip, etc. are likely
candidates (default: stop)
Value
TRUE if the package is installed, FALSE if it is not (invisibly)