[explorer] Add tags to the list of CREs

[dlicheva]

What is the issue?

The explorer could be improved to have more similar data and functionality to the original.

Expected Behaviour

The original CRE explorer here displays tags for the CREs ("OWASP Top 10 2021" for "Injection protection" ).

The explorer on OpenCRE.org should have them too.

Other related improvements:

• Users should be able to search by tag as well (e.g. search for "OWASP Top 10 2021" should return all relevant CREs)
• CRE style: The colour of the title and the name should be different, so the name is emphasized like this:
  
• List style: The grouped CREs should be collapsible