Setup

plugin.tx_picturecredits {
    view {
        templateRootPaths {
            0 = EXT:picturecredits/Resources/Private/Templates/
            1 = {$plugin.tx_picturecredits.view.templateRootPath}
        }
        layoutRootPaths {
            0 = EXT:picturecredits/Resources/Private/Layouts/
            1 = {$plugin.tx_picturecredits.view.layoutRootPath}
        }
        partialRootPaths {
            0 = EXT:picturecredits/Resources/Private/Partials/
            1 = {$plugin.tx_picturecredits.view.partialRootPath}
        }
    }
}

lib.picture_credits = USER_INT
lib.picture_credits {
    userFunc = TYPO3\CMS\Extbase\Core\Bootstrap->run
    extensionName = PictureCredits
    pluginName = PictureCredits
    controllerName = PictureCredit
}