Add advice on threat modelling, i.e. on how to create a config to avoid bloating the report

[DavidKorczynski]

Some reports are fairly bloated, e.g. showing data about many thousands of functions. This is currently addressed by making a configuration for specifying files to exclude from the report (https://github.com/ossf/fuzz-introspector/issues/116). It would be nice to have explicit suggestions in the report for config files that could help reduce the bloat of a report.