Leandro Souza

Fix broken doc links

3

This PR fixes broken links in the [docs/usage/extensibility/resource-definitions.md](https://github.com/json-api-dotnet/JsonApiDotNetCore/pull/1171/files#diff-fcf48abaccb657a94fde70e3b54f31c30faeb9f9608ac5dfb85927286fa8a3a8) file Closes #{ISSUE_NUMBER} #### QUALITY CHECKLIST - [ ] Changes implemented in code - [X] Complies with our [contributing guidelines](https://github.com/json-api-dotnet/JsonApiDotNetCore/blob/master/.github/CONTRIBUTING.md) - [...