Update project README

[enriquea]

• Create a README file in the repository where the dataset format and structure are described.
  - The description should include the structure of the Tab-Separate Value (TSV) file as the primary dataset structure input.
  - The interface with Spark Data Frame for Feature Selection (internal data structure used by the tool).
• Add to the README dataset file, the link to the Single-cell example we have been using for the benchmark of the algorithms.
  - Single-cell dataset: https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE156793
  - Include the formatted matrix used as input by the tool.

[enriquea]

@ypriverol Should we include the data description README (https://github.com/enriquea/fsspark/blob/main/README.data.md) in the project README?

[ypriverol]

I think a section summarizing the README.data.md and the proper link to it would be OK.

[enriquea]

This issue also can be closed!!