Provide a set of default report templates

[Xarthisius]

Provide a set of default templates as part of the package. They can be used by "name" instead of filepath.

How to test?

1. Deploy this branch
2. Confirm that tro-utils report --help displays:

   Options:
     -t, --template STRING_OR_PATH  Template file or one of the following:
                                    default  [required]
   

3. Using an example TRO, run report with -t default -o new.html
4. Download curl -LO https://raw.githubusercontent.com/craig-willis/trace-report/main/templates/tro.md.jinja2
5. Using the same example TRO, run report with -t tro.md.jinja2 -o old.html
6. Check that new.html is the same as old.html.