json-ld type formatting functions

[marc-portier]

to support not only ttl production, but also jsonld

helping out in the correct number formatting, and string-escaping

and following similar observations to those in #10

so maybe align the type-declarations and value-conformity-checking between both

[marc-portier]

consider looking into the exsiting jinja2 filter | tojson
see also https://jinja.palletsprojects.com/en/2.9.x/templates/#builtin-filters

• surely for delegating to production of nested structures
• but possibly also useful for single value formatting?

[marc-portier]

consider looking into the exsiting jinja2 filter | tojson see also https://jinja.palletsprojects.com/en/2.9.x/templates/#builtin-filters

• surely for delegating to production of nested structures

seems to work well for nested structures --> showcase in tests/templates/05-**