Abort / log an error if `Trunk.toml` is malformed

[benfrankel]

trafficstars

Currently trunk will silently ignore typos in Trunk.toml, even when running in --verbose mode. This makes it very difficult to even realize that there's an issue, let alone determine what the issue is and fix it.

For example, we had [server] instead of [serve] in our Trunk.toml and all the configs in that section were not working, but we didn't know why.

[ctron]

Yes, I can understand that.

The problem might be that serde doesn't support that easily: https://serde.rs/container-attrs.html#deny_unknown_fields

When using flatten (which IIRC we do) then this won't work. I am not really sure how to tackle this.