feat: add support for custom embedded folder and remove -d flag for daemon mode

[FilippoTrotter]

No description provided.

[puria]

In this way, by passing directly a folder via build, makes it impossible to have different directories as a source of contracts.
I do still prefer to have a simple file, with the directories one per line... or if you prefer a json... whatever simple when you run go generate you copy all of them.

[puria]

In this way, by passing directly a folder via build, makes it impossible to have different directories as a source of contracts. I do still prefer to have a simple file, with the directories one per line... or if you prefer a json... whatever simple when you run go generate you copy all of them.

Also if no directories as specified in this metadata extra_dir files, just the contract directory will be embedded. No need to have a different make build with extra arguments like dir={}