Add example assertions into the nf-test template

Description of feature

Could we add some example assertions, or at least a link to the help page on them?

                { assert snapshot(
                    process.out,
                    process.out.versions,
                    path(process.out.versions[0]).yaml
                    /* Examples of other assertions
                    file(process.out.bai[0][1]).name, // check file name only, assuming bai channel has a meta map
                    bam(process.out.bam[0][1]).getReadsMD5(), // summary of reads present in a bam file
                    path(process.out.vcf[0][1]).vcf.summary, // summary for variants in a vcf file
                    */
                ).match() }
            )
        }
``

Locate the nf-test template referenced by the issue and review its existing snapshot assertion example. Check the available assertion help alongside the template, then add representative assertion examples or a help-page link; done means the template gives users actionable assertion guidance.