Change example workflow from hello world to file processing

[georgiesamaha]

Workflow structure, data management is very different forr handling actual files compared with manipulating text strings. A working example with input files would allow:

• Demonstration how to enable singularity/docker
• Inputting a file from path
• Outputting >1 file
• Use of publishDir to output results to directory

Identified while testing Sydney-Informatics-Hub/fastqc-nf#5