Update project: mkdocs-exporter

[pawamoy]

In CI:

mkdocs-exporter:
     Missing entry point [mkdocs.plugins] 'exporter-pdf'.
     Instead got {'mkdocs.plugins': ['exporter']}

     Missing entry point [mkdocs.plugins] 'exporter-extras'.
     Instead got {'mkdocs.plugins': ['exporter']}

@adrienbrignon could you take a look 🙏?

[adrienbrignon]

Hello @pawamoy,

I have opened a PR (#231) to resolve the issue.
Thank you for your vigilance.