doc: add concept

README.md

@@ -6,4 +6,64 @@
 
 </div>
 
-Simple markup language сombining small file size and number of possibilities for describing the interface. Based on YAML.
+Simple markup language сombining small file size, big number of possibilities for describing the interface and readability.
+
+Specification is coming soon.
+
+## Concept
+
+```yaml
+h1: TxtDot revolution
+p: TxtDot is a cool project
+
+# {} for multiple objects
+row: {
+  {
+    h2: Features
+
+    ul: {
+      Server-side page simplification
+      Media proxy
+      Image compression with Sharp
+      Rendering client-side apps (Vanilla, React, Vue, etc) with webder
+      Search with SearXNG
+      Handy API endpoints
+      No client JavaScript
+      Some kind of Material Design 3
+      Customization with plugins, see @txtdot/sdk and @txtdot/plugins
+    }
+
+  }
+
+  {
+    h2: Running
+
+    {
+      h3: Dev
+
+      # () for multiline strings, indent is automatically trimmed
+      code: (
+        npm install
+        npm run dev
+      )
+    }
+
+    {
+      h3: Production
+
+      code: {
+        npm install
+        npm run build
+        npm run start
+      }
+    }
+
+    {
+      h3: Docker
+
+      code: docker compose up -d
+    }
+
+  }
+}
+```