Release leaflet.providers 3.0.0

[schloerke]

Prepare for release:

• git pull
• Check current CRAN check results
• Polish NEWS
• urlchecker::url_check()
• devtools::build_readme()
• devtools::check(remote = TRUE, manual = TRUE)
• devtools::check_win_devel()
• revdepcheck::revdep_reset()
• revdepcheck::revdep_check()
• Update cran-comments.md
• git push
• Draft blog post

Submit to CRAN:

• usethis::use_version('major')
• devtools::submit_cran()
• Approve email

Wait for CRAN...

• Accepted 🎉
• Finish & publish blog post
• Add link to blog post in pkgdown news menu
• usethis::use_github_release()
• usethis::use_dev_version(push = TRUE)
• Share on social media
• Slack link to blog post, bluesky, and linkedin in #open-source-comms