feat: provide check api

[antongolub]

Checks

To check the specified package version against the applied registry rules trigger its _check entrypoint.
For one package:

curl -X GET -k https://localhost:3000/registry/_check/eventsource/1.1.0
# {"[email protected]":"deny"}

To inspect a bulk on entries at once:

curl -X POST -k https://localhost:3000/registry/_check/bulk -d '["[email protected]"]'
# {"[email protected]":"deny"}

• New code is covered by tests
• All the changes are mentioned in docs (readme.md)