tests

Add instructions for running against customized TaskChampion #460

Job	Run time
Cargo Test	1m 20s
coverage	3m 13s
tests (Mac OS 13.latest)	0s
tests (Mac OS 12.latest)	0s
tests (Fedora 40, ubuntu-latest, fedora40)	3m 46s
tests (Fedora 41, ubuntu-latest, fedora41)	3m 58s
tests (Debian Testing, ubuntu-latest, debiantesting)	3m 43s
tests (Ubuntu 20.04, ubuntu-latest, ubuntu2004)	4m 8s
tests (Ubuntu 22.04, ubuntu-latest, ubuntu2204)	3m 52s
tests (OpenSUSE Tumbleweed (Rolling), ubuntu-latest, opensuse)	4m 3s
tests (Archlinux Base (Rolling), ubuntu-latest, arch)	3m 57s
	32m 0s

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