chore: add information about MJML

Author: d4vidsha

backend/README.md

@@ -198,3 +198,11 @@ alembic upgrade head
 ```
 
 If you don't want to start with the default models and want to remove them / modify them, from the beginning, without having any previous revision, you can remove the revision files (`.py` Python files) under `./backend/app/alembic/versions/`. And then create a first migration as described above.
+
+## Email Templates
+
+The email templates are in `./backend/app/email-templates/`. Here, there are two directories: `build` and `src`. The `src` directory contains the source files that are used to build the final email templates. The `build` directory contains the final email templates that are used by the application.
+
+Before continuing, ensure you have the [MJML extension](https://marketplace.visualstudio.com/items?itemName=attilabuti.vscode-mjml) installed in your VS Code.
+
+Once you have the MJML extension installed, you can create a new email template in the `src` directory. After creating the new email template and with the `.mjml` file open in your editor, open the command palette with `Ctrl+Shift+P` and search for `MJML: Export to HTML`. This will convert the `.mjml` file to a `.html` file and now you can save it in the build directory.