Add linter rule to verify links in documentation

### Clear and concise description of the problem

We include the spec docs in generated library and the [CI pipelines verify the URLs](https://github.com/Azure/azure-sdk-for-java/blob/main/eng/common/scripts/Verify-Links.ps1#L412-L416) used in the library. So, any invalid links in the spec will result in failing the library build.

We should do this link verification in the spec validation phase to detect invalid links early in the process.

For example, [this spec](https://github.com/Azure/azure-rest-api-specs/blob/ef3298cf2eddaff616e393a7e5fd69bc380a8bd0/specification/orbital/Microsoft.PlanetaryComputer/sas.tsp#L83) contains a link with `/en-us/` locale and fails the link validation for generated libraries.

### Checklist

- [x] Follow our [Code of Conduct](https://github.com/azure/typespec-azure/blob/main/CODE_OF_CONDUCT.md)
- [x] Check that this issue is about the Azure libraries for typespec. For feature request in the typespec language or core libraries file it in the [TypeSpec repo](https://github.com/Microsoft/TypeSpec/issues/new/choose)
- [x] Read the [docs](https://azure.github.io/typespec-azure/).
- [x] Check that there isn't already an issue that request the same feature to avoid creating a duplicate.

Start by reading the linked Verify-Links.ps1 checks and the example spec file specification/orbital/Microsoft.PlanetaryComputer/sas.tsp around line 83. Then locate the TypeScript spec validation entry point and determine how link failures should be reported; done means invalid documentation links are detected during spec validation rather than only during library builds.

Written by the indexing model from the issue text.