/**
 * Function to apply the environment variables onto your config object.
 * Matches the keys of the envVars with the config case insensitive, omits underscores `_` and matches nested objects in the config with dot separated keys in the envVars.
 * When dot notation in env is not available this can be done by a double underscore `__`.
 *
 * @param appSettings Imported json settings. A typed object with default or placeholder values
 * @param envVars Optional param to provide a custom list of environment variables. `process.env` by default.
 * @returns An object of the same type as the appSettings param where the values are replaced with the matching values of envVars.
 */
export declare const applyEnvConfig: <TConfig = {
    [key: string]: any;
}>(appSettings: TConfig, envVars?: {
    [key: string]: string;
}) => TConfig;