validate configuration

[FND]

Detecting typos and similar issues might save users from arduous rabbit holes (cf. faucet-pipeline/faucet-pipeline-sass#62). A recent example was the erroneous use of "exnext" causing significant confusion.

declepticon seems like an acceptable option for this:

import { validate, validators } from "declepticon";

validate(bundleConfig, {
    source: validators.nonBlankString
}, {
    onError(message) {
        throw new Error(message);
    }
});