Expose more variables to Jinja templates about reuse-tool HOT 1 OPEN

An issue this might address is the copyright date range issue from #915. merge_copyright_lines in _util.py uses spaces in the date range formatting:

                year = f"{min(years)} - {max(years)}"

When used in a template, there is no flexibility if one wanted to use what seems to be the far more common spaceless "YYYY-YYYY" range form:

{% for copyright_line in copyright_lines %}
{{ copyright_line }}
{% endfor %}

I'm not sure if more vars is the right approach for this particular issue. It might make the templates too complex? May need something to control the logic in the function that does the formatting.

from reuse-tool.