Some color variable definitions are missing

[rhysd]

Repro

Run

node ./cli.js --theme auto > test.css

and check the generated CSS content.

Expected behavior

All color variables used by styles are defined.

Actual behavior

CSS generated by the latest main branch of this repository is missing the following color variable definitions:

--color-fg-default: #e6edf3;
--color-fg-muted: #848d97;
--color-fg-subtle: #6e7681;
--color-canvas-default: #0d1117;
--color-canvas-subtle: #161b22;
--color-border-default: #30363d;
--color-border-muted: #21262d;
--color-neutral-muted: rgba(110,118,129,0.4);
--color-accent-fg: #2f81f7;
--color-accent-emphasis: #1f6feb;
--color-success-fg: #3fb950;
--color-success-emphasis: #238636;
--color-attention-fg: #d29922;
--color-attention-emphasis: #9e6a03;
--color-attention-subtle: rgba(187,128,9,0.15);
--color-danger-fg: #f85149;
--color-danger-emphasis: #da3633;
--color-done-fg: #a371f7;
--color-done-emphasis: #8957e5;

These defiinitions are included in github-markdown-css v5.5.1 so this is a regression after v5.5.1 release.