tox: pass more envs and set usedevelop=true

Author: RonnyPfannschmidt

tox.ini

@@ -2,10 +2,11 @@
 envlist=py{37,38,39,310,311,pypy37},docs,linting
 isolated_build = true
 [testenv]
+usedevelop=true
 deps=
     pytest
     pytest-timeout
-passenv = GITHUB_ACTIONS
+passenv = GITHUB_ACTIONS, HOME, USER, XDG_*
 commands=
     python -m pytest {posargs:testing}