Add support for auto-reload in run goal of function-maven-plugin

Jetty's maven plugin exposes a [`scan` parameter](https://github.com/jetty/jetty.project/blob/jetty-10.0.x/jetty-maven-plugin/src/main/java/org/eclipse/jetty/maven/plugin/JettyRunMojo.java#L67) for that purpose for example.

The main benefit would be developer efficiency on local environment. Also worth noting that Python supports a debug mode that auto-reloads.