Update _config.yml
Update _config.yml

amend slogan

Former-commit-id: 9340ab0fc4f76ca7a8138862d6568f64f801fea2 [formerly ed7e98ed9078d7e21d821076f597f69adc47aacf]
Former-commit-id: 81c75ebb078367e7c19df75ac72534b88fd42d4f
LibraryCarpentry/librarycarpentry.github.io,LibraryCarpentry/librarycarpentry.github.io,LibraryCarpentry/librarycarpentry.github.io