geobounds 1.0.0

• Changed the package software license from CC BY 4.0 to MIT and clarified that
  downloaded boundaries and included figures retain the licenses and attribution
  requirements of geoBoundaries and their original sources. Documentation
  now distinguishes the varying gbOpen licenses, UN OCHA terms and the
  non-commercial restriction on UN SALB boundaries. Downloads from
  gbAuthoritative now display a licensing notice.
• Made cache-related tests safer by isolating GEOBOUNDS_CACHE_DIR with
  withr::local_envvar() and using test-owned temporary cache directories with
  withr::local_tempdir().