* add jsdoc for crates fetch func
* add BaseCratesUserService for user stats api route
part of solution for #10614
* Add CratesUserDownloads service and tester
This commit adds the CratesUserDownloads service and tester files. The CratesUserDownloads service shows the user total downloads at Crates.io.
as requested by #10614
* render userid in code block
* add non-exsistent user CratesUserDownloads test
userid for API usage is int32, therefor to minimize chance of user taking the id used the max value for int32 is used.
* fixed typo