Update index.md
Update index.md

fix quotes

Former-commit-id: 0d84e37aa7574dc704ac69da5a2cc88eddd1234e [formerly c014e16f6d60fd867a827e3fede81a0a7037cf26]
Former-commit-id: 0e3c00d574516d9b2ddb426bda4d86b5e9ba4172
LibraryCarpentry/librarycarpentry.github.io,LibraryCarpentry/librarycarpentry.github.io,LibraryCarpentry/librarycarpentry.github.io