Update versions; fix CVE-2023-4863

[NJAldwin]

This updates minor and major versions:

• upgrading sharp to 0.33 resolves CVE-2023-4863 -- none of the breaking changes seem to be an issuse
• upgrading ava from 4 to 6 -- the main breaking change is renaming the files to skip watching
• upgrading eslint -- nothing major
• ugrading icojs -- 0.18 just removed support for old node; cannot go to 0.19 as that switches to ESM

The tests pass, so I think this is good to go.

This closes #10 as it resolves the CVE and updates more versions.