Dark theme and customization support

Hi!

What selectors do you mean? From a11y-light.css file?

Yes, exactly them. Now I completely override the style library of this module like this:

:root {
  --hphp-color-comment: #696969;
  --hphp-color-red: #d91e18;
  --hphp-color-orange: #aa5d00;
  --hphp-color-yellow: #aa5d00;
  --hphp-color-green: #008000;
  --hphp-color-blue: #007faa;
  --hphp-color-purple: #7928a1;
  --hphp-color-bg: #fefefe;
  --hphp-color-fg: #545454;
  --hphp-border: 4px solid #d4d4d8;
  --hphp-indent: 0.5em 0.5em 0.5em 20px;
}

.dark-mode {
  --hphp-color-comment: #d4d0ab;
  --hphp-color-red: #ffa07a;
  --hphp-color-orange: #f5ab35;
  --hphp-color-yellow: #ffd700;
  --hphp-color-green: #abe338;
  --hphp-color-blue: #00e0e0;
  --hphp-color-purple: #dcc6e0;
  --hphp-color-bg: #2b2b2b;
  --hphp-color-fg: #f8f8f2;
  --hphp-border: 4px solid #43454a;
}

/* Comment */
.hljs-comment,
.hljs-quote {
  color: var(--hphp-color-comment);
}

/* Red */
.hljs-variable,
.hljs-template-variable,
.hljs-tag,
.hljs-name,
.hljs-selector-id,
.hljs-selector-class,
.hljs-regexp,
.hljs-deletion {
  color: var(--hphp-color-red);
}

/* Orange */
.hljs-number,
.hljs-built_in,
.hljs-builtin-name,
.hljs-literal,
.hljs-type,
.hljs-params,
.hljs-meta,
.hljs-link {
  color: var(--hphp-color-orange);
}

/* Yellow */
.hljs-attribute {
  color: var(--hphp-color-yellow);
}

/* Green */
.hljs-string,
.hljs-symbol,
.hljs-bullet,
.hljs-addition {
  color: var(--hphp-color-green);
}

/* Blue */
.hljs-title,
.hljs-section {
  color: var(--hphp-color-blue);
}

/* Purple */
.hljs-keyword,
.hljs-selector-tag {
  color: var(--hphp-color-purple);
}

.hljs {
  overflow-x: auto;
  display: block;
  padding: var(--hphp-indent);
  color: var(--hphp-color-fg);
  white-space: pre;
  background: var(--hphp-color-bg);
  border-inline-start: var(--hphp-border);
}

.hljs-emphasis {
  font-style: italic;
}

.hljs-strong {
  font-weight: bold;
}

But it would be great if a dark theme could be created by simply overriding variables by extending the existing library in the theme.