Adding data for example task

[neelguha]

This pull-request is intended to illustrate how to add data to LegalBench.

1. Create a folder under tasks/ with the dataset name.
2. In this folder, add train.tsv, test.tsv, and base_prompt.txt. Add README.md, filling out the information that we've highlighted in this PR.
3. Add the dataset name to the table in tasks/README.md.
4. Add your name as a contributor to the contributors section of the main README.md