Add post navigation

Signed-off-by: Nikolaos Karaolidis <nick@karaolidis.com>

assets/sass/postnav.scss

@@ -0,0 +1,59 @@
+.postnav {
+  max-width: $width-content;
+  margin: 0 auto;
+  padding: 2rem;
+
+  display: flex;
+  justify-content: space-between;
+  gap: 1rem;
+
+  a {
+    flex: 50%;
+    color: inherit;
+  }
+
+  a:hover {
+    color: var(--text-800);
+  }
+
+  p {
+    margin: 0.5rem 0 0.5rem 0;
+  }
+
+  .caption {
+    font-weight: 500;
+  }
+
+  .title {
+    overflow-wrap: break-word;
+    word-break: break-word;
+  }
+
+  .next {
+    text-align: right;
+  }
+
+  .previous .caption::before {
+    content: "‹ ";
+  }
+
+  .next .caption::after {
+    content: " ›";
+  }
+}
+
+.content + .postnav {
+  padding-top: 0;
+}
+
+@media (max-width: $width-mobile) {
+  .postnav {
+    padding: 1rem;
+
+    flex-direction: column;
+
+    a {
+      flex: auto;
+    }
+  }
+}