docs: add configuration section for environment variables in README

Author: ErwanDecoster

README.md

@@ -6,6 +6,40 @@ This is the source repository of the [iExec documentation](https://docs.iex.ec)
 
 - Node 22
 
+## Configuration
+
+### Environment Variables (Optional)
+
+Some features of the application require environment variables. This
+configuration is optional and only needed if you plan to work with Hello World
+pages. Create a `.env` file at the root of the project using the provided
+`.env.example` as a template:
+
+```bash
+cp .env.example .env
+```
+
+Then fill in the required values:
+
+```env
+VITE_REOWN_PROJECT_ID=your_project_id_here
+```
+
+#### Getting your VITE_REOWN_PROJECT_ID
+
+To obtain your `VITE_REOWN_PROJECT_ID`, follow these steps:
+
+1. Go to [https://dashboard.reown.com/](https://dashboard.reown.com/)
+2. Create an account if you don't have one already
+3. Once logged in, click on "Create Project" or "New Project"
+4. Fill in your project information:
+   - Project name
+   - Description (optional)
+   - Website URL (optional)
+5. Once the project is created, copy the "Project ID" displayed in the project
+   details
+6. Paste this ID in your `.env` file as the value for `VITE_REOWN_PROJECT_ID`
+
 ## Run app
 
 ```