Text and console reporters links to non-existing documentation pages for plugins

[mjpieters]

Describe the bug

When using a plugin (such as jupyfmt, several reporters output links to a non-existing page.

E.g. the text reporter:

Results of jupyfmt linter (version 0.5.1)
See documentation on https://megalinter.github.io/descriptors/jupyter_jupyfmt/

and the console reporter:

- Using [jupyfmt v0.31.0] https://megalinter.github.io/v5/descriptors/jupyter_jupyfmt

To Reproduce
Steps to reproduce the behavior:

1. Create a minimal setup:

   cd $(mktemp -d -t mcve-XXXXXXXXXX)
   cat > .mega-linter.yaml <<EOF
   PLUGINS:
     - https://raw.githubusercontent.com/kpj/jupyfmt/master/mega-linter-plugin-jupyfmt/jupyfmt.megalinter-descriptor.yml
   ENABLE:
     - JUPYTER
   EOF
   touch dummy.ipynb  # so the linter has something to run against

2. Run npx mega-linter-runner

The console output will include:

### Processed [JUPYTER] files
- Using [jupyfmt v0.5.1] https://megalinter.github.io/v5/descriptors/jupyter_jupyfmt

and in report/linters_logs/WARNING-JUPYTER_JUPYFMT.log:

Results of jupyfmt linter (version 0.5.1)
See documentation on https://megalinter.github.io/descriptors/jupyter_jupyfmt/

Expected behavior

Either no documentation URL should be shown, or it should be possible for the plugin to define a URL, with a possible fallback to the linter_url value.

[nvuillam]

That's right, MegaLinter plugins should redirect to the plugin documentation, i'll try to arrange that :)

[nvuillam]

@mjpieters it should be ok now (with beta version) :)