Improve accordion docs examples and button line height (#3076)

.changeset/accordion-button-line-height.md

@@ -0,0 +1,5 @@
+---
+"@tabler/core": patch
+---
+
+Updated `.accordion-button` line height to `1.25rem` via the `--tblr-accordion-btn-line-height` variable.

.changeset/docs-accordion-bg-surface.md

@@ -0,0 +1,5 @@
+---
+"@tabler/docs": patch
+---
+
+Updated accordion docs examples to use `.bg-surface` on each `.accordion-item`.