Remove dependencies (request, request-promise)

[ddugovic]

I was about to start using this module with my project when I noticed this library has many dependencies instead of using node's built-in fetch():

npm install lichess-client
npm WARN deprecated har-validator@5.1.5: this library is no longer supported
npm WARN deprecated request-promise@4.2.6: request-promise has been deprecated because it extends the now deprecated request package, see https://github.com/request/request/issues/3142
npm WARN deprecated uuid@3.4.0: Please upgrade  to version 7 or higher.  Older versions may use Math.random() in certain circumstances, which is known to be problematic.  See https://v8.dev/blog/math-random for details.
npm WARN deprecated request@2.88.2: request has been deprecated, see https://github.com/request/request/issues/3142

added 53 packages, and audited 75 packages in 4s

I'll be fine using fetch() instead of using an API wrapper, but I thought I'd pass along this information for future consumers.