Enhance UX in OpenPeerReview: Group metadata fields

[jh-RLI]

Description of the issue

All fields are currently displayed independently of each other:

Fields: GeneralTab - Context (Object), Keywords (List), Language (List)

Spatial&TemporalTab - Timeseries (List of Objects)

SourcesTab - Source (List of Objects)

Ideas of solution

Group all fields together that belong to the same object (like source 1, 2, 3 ....)

Workflow checklist

• [ ] I am aware of the workflow in CONTRIBUTING.md

[bmlancien]

Mockup of how the content inside the General tab could look like.