Switch from riskmetric to val.meter #8

Currently the pipeline and the repository is using riskmetric to measure packages.
We need to measure with val.meter to move to the new tools.

From the feedback we got:

Outdated Template in {val.report}: When testing the workflow on a custom package following the guide, the {val.report} template still uses riskmetric::pkg_assess(). It should be updated to use the new val.meter::pkg() object, as {val.meter} is the intended successor to riskmetrics

In addition reports should be generated with val.report from the val.meter scores (not riskmetrics).