Add styles for complex layout tables

When there are tables that have rowspan header cells, avoid making those
tables stripy (override Docsy here). Also customize how the table is
laid out.

assets/scss/_custom.scss

@@ -45,6 +45,30 @@ body {
   }
 }
 
+/* Complex table layout support */
+
+.td-content, body.td-content {
+  table.complex-layout {
+    tbody tr,
+    tbody tr:nth-of-type(2n+1) {
+      /* Avoid stripes */
+      background-color: initial;
+    }
+    tbody tr:not(:last-child) > td[colspan] {
+      /* provide a visual break between rows */
+      padding-bottom: 1.5em;
+    }
+    tbody > tr > th[scope="row"]:first-child {
+      min-width: 9em;
+    }
+    tbody > tr > th[rowspan] {
+      vertical-align: middle;
+    }
+    border-collapse: separate;
+    border-spacing: 0 0;
+    max-width: calc(max(min(100vw, 110%), 40vw));
+  }
+}
 
 /* Emphasize first paragraph of running text on site front page */
 body.td-home main[role="main"] > section:first-of-type .content p:first-child {