init(docs): create docs site template with Fumapress and Waku

docs/source.config.ts

@@ -0,0 +1,11 @@
+import { defineConfig, defineDocs } from "fumadocs-mdx/config";
+
+export const docs = defineDocs({
+  dir: "content/docs",
+  docs: {
+    // Required by fumapress' llms.txt plugin (getText("processed")).
+    postprocess: { includeProcessedMarkdown: true },
+  },
+});
+
+export default defineConfig();