Fix for CRAN checks.

• Compatible with ipaddress 1.0.0.

• Compatible with latest {ggplot2}. This introduced a breaking change, where an aesthetic of geom_hilbert_outline() was renamed from size to linewidth.
• Use {cli} to format error messages.

Minor changes for compatibility with latest {tidyselect}.

Resolve CRAN check notes about HTML5 by upgrading to latest {roxygen}.

• A new layer geom_hilbert_outline() can overlay the outline of the Hilbert curve. This can guide the eye to regions that are close in IP address space (#16).
• Improved performance of stat_summary_address(), by using an alternative check for missing values (#15).
• stat_summary_address() now removes data that were not mapped to the 2D grid (because the address was outside the visualized network). A warning is generated by default, which can be disabled using the na.rm argument. This new behavior is consistent with that of native ggplot2 layers (#15).

First CRAN release.

• coord_ip() provides a unified mapping from IP address space to the 2D grid.
• stat_summary_address() summarizes IP addresses on a heatmap.
• theme_ip_light() and theme_ip_dark() offer sensible default theming for ggip plots.