Release dcm2 1.0.0

[JeffreyCHoover]

First release:

• usethis::use_cran_comments()
• Update (aspirational) install instructions in README
• Proofread Title: and Description:
• Check that all exported functions have @return and @examples
• Check that Authors@R: includes a copyright holder (role 'cph')
• Check licensing of included files
• Review https://github.com/DavisVaughan/extrachecks

Prepare for release:

• git pull
• Check if any deprecation processes should be advanced, as described in Gradual deprecation
• devtools::build_readme()
• urlchecker::url_check()
• devtools::check(remote = TRUE, manual = TRUE)
• devtools::check_win_devel()
• rhub::check_for_cran()
• rhub::check(platform = 'ubuntu-rchk')
• rhub::check_with_sanitizers()
• git push
• Draft blog post

Submit to CRAN:

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

Wait for CRAN...

• Accepted 🎉
• git push
• usethis::use_github_release()
• usethis::use_dev_version()
• usethis::use_news_md()
• git push
• Finish blog post
• Tweet
• Add link to blog post in pkgdown news menu