Docs: new documentation site (#2723)

This commit adds a VitePress build to the main repository,
aiming to ditch GitHub Wiki. Moving further, we're going to
host our own documentation site eithor on GitHub Pages or
something alike.

docs/premium/the-profiling-engine.md

@@ -0,0 +1,13 @@
+---
+sidebarTitle: "Feature: The Profiling Engine"
+sidebarOrder: 8
+---
+
+# The Profiling Engine
+
+https://github.com/Dreamacro/clash-tracing
+
+```yaml
+profile:
+    tracing: true
+```