Create trainers.md
Create trainers.md

initial commit

Former-commit-id: 228e9b23432ebba0e4e22175e6f6269de0f8a8df [formerly e30c815ea4a67e52113f5da2f47a7dc3af7426d3]
Former-commit-id: 10aeeb3eab601388901029d93031f927ea4fea7a
LibraryCarpentry/librarycarpentry.github.io,LibraryCarpentry/librarycarpentry.github.io,LibraryCarpentry/librarycarpentry.github.io