Add Salt 3006.0 and py3.9/py3.10

Adds 3006.0 to versions of Salt tested against and also python 3.9 and
3.10

.github/workflows/test.yaml

@@ -15,12 +15,15 @@ jobs:
         py:
           - "3.7"
           - "3.8"
+          - "3.9"
+          - "3.10"
         netapi:
           - "cherrypy"
           - "tornado"
         salt:
           - "v3004.2"
           - "v3005.1"
+          - "v3006.0"
           - "master"
     steps:
       - name: Setup python for test ${{ matrix.py }}

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = py{3.7,3.8}-{cherrypy,tornado}-{v3004.2,v3005.1,master},coverage,flake8
+envlist = py{3.7,3.8,3.9,3.10}-{cherrypy,tornado}-{v3004.2,v3005.1,v3006.0,master},coverage,flake8
 skip_missing_interpreters = true
 skipsdist = false
 
@@ -9,7 +9,8 @@ deps = -r{toxinidir}/tests/requirements.txt
     v3004.2: salt<3004.2
     v3004.2: jinja2<3.1
     v3005.1: salt<3005.1
-    py3.7-{cherrypy,tornado}-{v3004.2,v3005.1}: importlib-metadata<5.0.0
+    v3006.0: salt<3006.0
+    py3.7-{cherrypy,tornado}-{v3004.2,v3005.1,v3006.0}: importlib-metadata<5.0.0
     master: git+https://github.com/saltstack/salt.git@master#egg=salt
 
 changedir = {toxinidir}