Update the Contribution part of the documentation

[eibar-flores]

In the contribute part of the documentation, the Image link is broken. In addition, the base IRI needs to be updated to the w3c PURLs

To Reproduce
Steps to reproduce the behavior:

1. Go to Contribute
2. Navigate to "Propose additions/deletion of elements"
3. See broken image of "Protege config"
4. See outdated IRI in “Specified IRI” for you to copy: https://emmo.info/battery#

Expected behavior
The Image should be visible, and updated with the W3C PURLs
The "Specified IRI" for Protege should be updated with the W3C PURLs: https://w3id.org/emmo/domain/<domain>#, where <domain> should be replaced by electrochemistry, battery, chemicalsubstance, etc.

Screenshots