Lower warnings to debug

[0x0f0f0f]

I have an application that uses ExpressionExplorer.jl to navigate large Julia codebases and make reactive nodes. In some cases we have complex macro calls and expressions in DSLs that it fails to compute a ReactiveNode for.

This results in many warning being printed in the console whenever we run it

This PR lowers the @warn statements to @debug in order to leave the stderr clean

[Pangoraw]

Could you wrap the ExpressionExplorer invocation with a NullLogger ? These warnings have proven helpful in the past to detect unhandled patterns. For context, Pluto does not pass macrocalls so it has fewer unhandled cases like this.