Add README file

[toymachiner62]

I came here through this link and the first thing I notice is that there is no README.md file with instructions on how to use this API or even a link to your API docs located here.

Please add a README.md file and at a minimum point people in the direction of your documentation.

[futo82]

The API is actively being supported at https://github.com/CBIIT/ctrp-clinical-trials-api. A README exists with a URL to the API's documentation (https://clinicaltrialsapi.cancer.gov/).