init(Docs): add docs site based on Fumapress and Fumadocs

Docs/src/app.css

@@ -0,0 +1,9 @@
+@import "tailwindcss";
+@import "fumadocs-ui/css/neutral.css";
+@import "fumadocs-ui/css/preset.css";
+@import "fumapress/css/preset.css";
+
+@theme {
+  --font-mono: "JetBrains Mono", monospace;
+  --default-font-family: "Geist", sans-serif;
+}