Publish Validator Release 5.0

[emmambd]

It's time for a new validator release!

To do:

• [x] Publish the release following the steps in RELEASE.md (Jean-Claude)
• [ ] Send the release e-mail to users that asked to be informed via e-mail (Emma)
• [ ] Blog post (Emma)

[jcpitre]

Releasing is done. Did everything in RELEASE.md. But:

• I had to upload the installers zip files by hand as the GH action does not do it (see https://github.com/MobilityData/gtfs-validator/issues/1719)
• I had to publish the jars be hand on the terminal since the publish_assets.yml GH action executed the publish seemingly successfully but nothing appeared in Sonatype.