Release shinychat 0.3.0

[gadenbuie]

Prepare for release:

• git pull
• Check current CRAN check results
• Advance deprecations, if needed
• Polish NEWS
• urlchecker::url_check()
• devtools::check(remote = TRUE, manual = TRUE)
• devtools::check_win_devel()
• devtools::check_mac_release()
• revdepcheck::cloud_check()
• Update cran-comments.md
• git push
• Draft blog post
• Check that shinychat js assets are up-to-date (make js-build && make r-update-dist)
• Set development.mode: auto in pkg-r/pkgdown/_pkgdown.yml and remove this release bullet.
• fix(markdown-stream): Scroll to bottom when tool request/results finish rendering #157

Submit to CRAN:

• usethis::use_version('minor')
• 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