feature to add custom field in the resumes

Right now we have five fields which users can enter to generate resume user details , experience , projects , achievements and skills , we should be able to add custom fields like certificates etc.
Design a route to handle custom fields requested by users and generate required frontend pages and add to resume template.

Start by mapping how the existing user details, experience, projects, achievements, and skills fields flow from the Flask routes through the frontend and resume template. Define the custom-field data model and page flow before implementation; done means users can add fields such as certificates and the generated resume includes them.

Written by the indexing model from the issue text.