docs(readme): add content structure and theme customization sections

README.md

@@ -1,14 +1,42 @@
 # miti99
 
-Source code of my personal blog at [miti99.com](https://miti99.com), built with [Hugo](https://gohugo.io) and the [Stack](https://github.com/CaiJimmy/hugo-theme-stack) theme.
+Source of [miti99.com](https://miti99.com) — personal blog (VN/EN) built with [Hugo](https://gohugo.io) and the [Stack](https://github.com/CaiJimmy/hugo-theme-stack) theme.
 
 ## Quick start
 
 ```bash
 git submodule update --init --recursive
-hugo server
+hugo server -D
 ```
 
+Site available at `http://localhost:1313`.
+
+## Content structure
+
+Posts live under `content/post/YYYY/MM/DD/index.md`. Each post is a Hugo leaf bundle — images and assets sit next to `index.md` in the same directory.
+
+```
+content/
+  post/
+    2024/
+      03/
+        15/
+          index.md     ← post content (Vietnamese / English)
+          cover.jpg    ← optional cover image
+  page/                ← standalone pages (about, projects, …)
+```
+
+## Theme customization
+
+Theme config lives in `config/` (Hugo config directory split). Key overrides:
+
+- `config/_default/params.toml` — sidebar, avatar, footer, color scheme
+- `config/_default/menu.toml` — navigation links
+- `assets/` — custom CSS/JS overrides loaded on top of the Stack theme
+- `layouts/` — template overrides (add a file here to override any Stack partial)
+
+The Stack theme is pulled in as a git submodule under `themes/hugo-theme-stack/`.
+
 ## License
 
 Apache-2.0 — see [LICENSE](LICENSE).