Add a light and dark theme toggle

The button is emitted hidden and only revealed by the script, so a
browser without JavaScript never shows a control that cannot work and
the page keeps tracking the system theme.

1 file changed, 3 insertions, 0 deletions

diff --git a/source/ui-shared.c b/source/ui-shared.c
index 83454fe..88e5075 100644
--- a/source/ui-shared.c
+++ b/source/ui-shared.c
@@ -1082,6 +1082,9 @@ static void print_header(void)
 		html_txt(ctx.cfg.root_desc);
 		html("</p>\n");
 	}
+
+	html("<button type='button' class='theme-toggle' hidden "
+	     "aria-label='Toggle color theme'></button>\n");
 	html("</header>\n");
 }