docs: 引入 Fumadocs

ci: set up github actions

docs/lib/layout.shared.tsx

@@ -0,0 +1,19 @@
+import type { BaseLayoutProps } from 'fumadocs-ui/layouts/shared';
+
+/**
+ * Shared layout configurations
+ */
+export function baseOptions(): BaseLayoutProps {
+  return {
+    githubUrl: 'https://github.com/nagisa77/OpenIsle',
+    nav: {
+      title: 'OpenIsle Docs',
+      url: '/docs',
+    },
+    searchToggle: {
+      enabled: false,
+    },
+    // see https://fumadocs.dev/docs/ui/navigation/links
+    links: [],
+  };
+}