Add developer docs.

README.md

@@ -1,4 +1,4 @@
-# use-markdown
+# @nulib/use-markdown
 
 React hook for handling of Markdown in web applications with support for [GitHub flavored markdown](https://github.github.com/gfm/) content.
 
@@ -27,3 +27,22 @@ const MyComponent = () => {
 
 export default MyComponent;
 ```
+
+## Development
+
+Run in development environment.
+
+```sh
+npm i
+npm run dev
+```
+
+A browser session will begin:
+
+```sh
+  VITE v5.2.8  ready in 84 ms
+
+  ➜  Local:   http://localhost:5173/
+  ➜  Network: use --host to expose
+  ➜  press h + enter to show help
+```