chore(datasource): add more type annotations (#4312)

lib/datasource/cargo/index.ts

lib/datasource/common.ts

lib/datasource/dart/index.ts

lib/datasource/docker/index.ts

lib/datasource/git-tags/index.ts

lib/datasource/github/index.ts

lib/datasource/gitlab/index.ts

lib/datasource/go/index.ts

lib/datasource/hex/index.ts

lib/datasource/index.ts

lib/datasource/npm/get.ts

lib/datasource/npm/npmrc.ts

lib/datasource/npm/releases.ts

lib/datasource/nuget/index.ts

lib/datasource/nuget/v2.ts

lib/datasource/nuget/v3.ts

lib/datasource/orb/index.ts

lib/datasource/packagist/index.ts

lib/datasource/pypi/index.ts

lib/datasource/rubygems/get-rubygems-org.ts