add pypy37 to envlist

Author: RonnyPfannschmidt

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist=py{37,38,39,310,311},docs,linting
+envlist=py{37,38,39,310,311,pypy37},docs,linting
 isolated_build = true
 [testenv]
 deps=
@@ -23,7 +23,6 @@ commands =
 
 [testenv:linting]
 skip_install = True
-basepython = python3
 deps = pre-commit>=1.11.0
 commands = pre-commit run --all-files --show-diff-on-failure