miscellanous information

copy of https://github.com/equinor/dot-archive/issues/790

> Is your feature request related to a problem? Please describe.
The decision project can better documented with some free form information, such as text and figures. Having a dedicated tab for this would be beneficial.

Alternatively the project description form could be a bigger block and could take some e.g. markdown text.

Further https://github.com/equinor/dot-archive/issues/702

> Is your feature request related to a problem? Please describe.
It may be useful to link the project to some background information, such as figures, documents and so on.
We could add a "background" field to the project data model containing:
>
> - text
> - figures
> - links to other documents
>
> If the background information needs to be very precise, the text may have to be formatted, including tables, and text structure

No files, tests, or entry points are named. Start by tracing the project data model and API, then clarify whether the work is a dedicated information tab or expanded description/background data; done should support the agreed text, figures, document links, and formatting scope.

Written by the indexing model from the issue text.