`contentlayer.config.ts` should handle tsconfig paths

using an absolute import defined via `tsconfig.json#paths` in `contentlayer.config.ts` currently throws a `ConfigReadError`

steps to reproduce:
- `git clone git@github.com:stefanprobst/issue-contentlayer-tsconfig-paths.git`
- `cd issue-contentlayer-tsconfig-paths`
- `npm i`
- `npm run generate`