Release grateful 0.2.0

[Pakillo]

First release:

• [x] usethis::use_cran_comments()
• [x] Update (aspirational) install instructions in README
• [x] Proofread Title: and Description:
• [x] attachment::att_amend_desc()
• [x] Check that all exported functions have @return and @examples
• [x] Check that Authors@R: includes a copyright holder (role 'cph')
• [x] Check licensing of included files
• [x] Review https://github.com/DavisVaughan/extrachecks
• [x] spelling::spell_check_package() or devtools::spell_check()
• [x] devtools::run_examples()
• [x] devtools::test_coverage()
• [x] goodpractice::gp()
• [x] rcmdcheck::rcmdcheck(args = c("--no-manual", "--as-cran"))

Prepare for release:

• [x] git pull
• [x] devtools::build_readme()
• [x] urlchecker::url_check()
• [x] devtools::check(remote = TRUE, manual = TRUE)
• [x] devtools::check_win_devel()
• [x] devtools::check_mac_release()
• [x] devtools::check_rhub() or rhub::check_for_cran()
• [x] update cran_comments
• [x] git push

Submit to CRAN:

• [x] devtools::release()
• [x] Approve email

Wait for CRAN...

• [x] Accepted :tada:
• [x] git push
• [ ] usethis::use_github_release()
• [x] usethis::use_dev_version()
• [x] git push