loader(config, loader, forRule = undefined) {
            return {
                exists: () => t.truthy(findWebpackLoader(config, loader, forRule)),
                absent: () => t.falsy(findWebpackLoader(config, loader, forRule)),
                get: () => findWebpackLoader(config, loader, forRule)
            };
        }
Assert that a rule with the given loader can be found

@param {import("webpack").Configuration} config
@param {string|RegExp|((loader: string) => boolean)} loader
@param {import('webpack').RuleSetRule|undefined} [forRule]