move css into separate files

_includes/footer.css

@@ -0,0 +1,30 @@
+footer {
+  border-top: 1px dotted rgba(0,0,0,.15);
+  padding: 4rem 0;
+}
+
+#footerNav ul {
+  margin: 0;
+  padding: 0;
+  display: flex;
+  gap: 1em;
+}
+
+#footerNav li {
+  display: inline;
+}
+
+.footer-container {
+  max-width: var(--page-width);
+  margin-left: auto;
+  margin-right: auto;
+  display: grid;
+  grid-template-columns: auto auto;
+  grid-auto-flow: column;
+  grid-template-rows: 1fr 1fr;
+  gap: 1em;
+}
+
+.footer-container > :nth-last-child(-n + 2) {
+  text-align: end;
+}