Move all the root styles to fragment files

Create assets/styles/root to hold all the fragments of the root
stylesheet. This should make it easier to find and hack on style. Yay!

assets/styles/root/050_site_footer.css

@@ -0,0 +1,40 @@
+@layer root {
+    footer.site {
+        align-items: center;
+        display: flex;
+        flex-direction: column;
+        margin-block: var(--body-item-spacing);
+        text-align: center;
+    }
+
+    footer.site > ul {
+        align-items: center;
+        display: flex;
+        flex-wrap: wrap;
+        justify-content: center;
+        list-style: none;
+    }
+
+    footer.site > .slogans {
+        margin-block-end: 0;
+    }
+
+    footer.site > .slogans > li {
+        margin-block-end: 0;
+        margin-inline-start: 0.5em;
+    }
+
+    footer.site > p {
+        margin: 0;
+    }
+
+    footer.site p + p {
+        margin-top: 0.25rem;
+    }
+
+    @media (max-width: 740px) {
+        footer.site .slogans span {
+            white-space: nowrap;
+        }
+    }
+}