Comprehensive Update to Harvesters, CSS, and More

[mjanez]

This PR encompasses a wide range of updates and improvements across multiple areas of the project.

• Updated the field_mapping library for improved harvester validation and made enhancements to the harvesters.
• Fixed the contact_info and publisher_info snippets.
• Updated the README for the gspread/onedrive harvester.
• Improved the get_ckan_format configuration and fixed URL validation in SchemingDCATHarvester.
• Fixed the icon class for the university publisher type and made improvements to URL fields.
• Updated geodcatap_es_dataset.yaml with additional language options and updated language settings for Spanish.
• Made improvements to CSS code, including the addition of block-code style.
• Added a display snippet for spatial JSON in default presets.
• Updated the link schema class name to 'link-list' and implemented filter choices.
• Updated URL handling in SchemingDCATHarvester and removed logs.
• Added a metadata templates sidebar for the schemingdcat_xls harvester.
• Refactored schemingdcat_info.html to handle empty list values.

These changes aim to improve the overall functionality, user experience, and code quality of the project.