Use a `collapsed` table style in the HTML stylesheet

styles/rst2html_githublike_fzj.css

@@ -1087,6 +1087,16 @@ span.section-subtitle {
   font-size: 80%
 }
 
+table {
+  border-collapse: collapse
+}
+
+table,
+th,
+td {
+  border: 1px solid
+}
+
 table.citation {
   border-left: solid 1px gray;
   margin-left: 1px