feat: separated content meta (#929)

to allow for CSS styling

quartz/components/styles/contentMeta.scss

@@ -0,0 +1,14 @@
+.content-meta {
+  margin-top: 0;
+  color: var(--gray);
+
+  &[show-comma="true"] {
+    > span:not(:last-child) {
+      margin-right: 8px;
+
+      &::after {
+        content: ",";
+      }
+    }
+  }
+}