Make collapse/display templates work in dark mode

In dark mode, the display templates still have a light background, and stand
out far too much. This adds CSS to change the `bg-light` class for the collapse
and display templates to the dark-mode colors when `data-bs-theme=dark`.

See jhpyle/docassemble#718 for a discussion on a
suggested fix for a similar issue, which resulted in the suggested workaround
here.

docassemble/ALToolbox/data/static/collapse_template.css

@@ -28,4 +28,13 @@
 .al_collapse_template a.collapsed .pdcaretclosed,
 .al_display_template a.collapsed .pdcaretclosed {
     display: inline;
-}
+}
+
+/* An upstream fix for Bootstrap's lack of a dark/light mode neutral style.
+   See https://github.com/jhpyle/docassemble/pull/718 */
+[data-bs-theme=dark] .al_collapse_template .bg-light,
+[data-bs-theme=dark] .al_display_template .bg-light,
+[data-bs-theme=dark] .al_display_template.bg-light {
+  --bs-bg-opacity: 1;
+  background-color: rgba(var(--bs-dark-rgb), var(--bs-bg-opacity)) !important;
+}