Prepare 0.8.4 release

[kanru]

• [x] Review issues list
• [x] Make sure NEWS is updated
• [x] Update version numbers in
  • [x] CMakeLists.txt
  • [x] Cargo.toml, */Cargo.toml
• [x] Update Cargo.lock
• [x] Prepare pre-release/release tarball

  cmake --preset rust
  cmake --build build -t package_source

  • [x] Verify the content of the tarball
• [x] Git tag and sign tag
• [x] cargo publish
• [x] Tag new release on GitHub
• [x] Update website
• [x] Send announcement