Improve the package.json scripts

1. Include a `prestart` script, which runs the build
2. Make the `start` script just start the demo server
3. Add a new `dev` script, which contains the nodemon logic
4. nodemon now watches for changes in `*.ts` files and runs the start command

Signed-off-by: Antonis Kalipetis <akalipetis@gmail.com>

.gitignore

@@ -12,3 +12,4 @@ npm-debug.log
 /.idea/
 .env
 build/
+.vscode/