Functions: Added support for Node.js 20

Nhost has introduced the option to select either Node.js 18 or Node.js 20 as the runtime for functions, allowing users to easily specify their preferred version in the nhost.toml configuration file. This feature can be implemented by adjusting the version number in the configuration and verifying the runtime through command-line tools. The addition aims to streamline the process of harmonizing runtime environments and simplifying user setups, with further information available in the documentation.