Set dynamic env variables in config file

Added an example demonstrating how to set environment variables in the Vite config file.

Included a dynamic setup for the latest Git commit hash (VITE_CODE_VERSION) as an environment variable using execSync. This ensures the app can reference the commit hash during build time

docs/config/index.md

@@ -115,3 +115,21 @@ export default defineConfig(({ mode }) => {
   }
 })
 ```
+
+## Setting Environment Variables inside Config file
+
+Use the define block in Vite to inject global constants or environment variables accessible within the application at build time. While `.env` files should always be used for static variables, dynamic values like the latest Git commit hash can also be set.
+
+```js twoslash
+import { defineConfig } from "vite";
+import { execSync } from "child_process";
+
+export default defineConfig({
+  define: {
+    // Make the commit hash available as an env varaible in your app
+    "import.meta.env.VITE_CODE_VERSION": JSON.stringify(
+      execSync("git rev-parse HEAD").toString().trim()
+    ),
+  },
+});
+```