Improve tox file

tox.ini

@@ -3,14 +3,10 @@ min_version = 4.0
 env_list = py3{9,10,11,12,13}
            pypy{310,311}
            graalpy
-           flake8, black, typecheck
-labels =
-    test = py3{9,10,11,12,13},pypy{310,311},graalpy
-    cpy = py3{9,10,11,12,13}
-    pypy = pypy{310,311}
-    check = flake8, black, typecheck
+           check, format, typecheck
 
 [testenv]
+labels = test
 # wheel install
 package = wheel
 # wheel is universal so can use the same wheel for all envs
@@ -25,28 +21,43 @@ deps =
 commands =
     pytest -Werror --doctest-glob="*.rst" {posargs}
 
-[testenv:py3{9,10,11,12}]
+[testenv:py3{9,10,11,12,13}]
+labels = test, cpy
 deps =
      pytest
      pyyaml
      google-re2
      ua-parser-rs
      ./ua-parser-builtins
 
-[testenv:flake8]
+[testenv:pypy{310,311}]
+labels = test, pypy
+
+[testenv:check]
+labels = check
 package = skip
 deps = ruff
 commands = ruff check {posargs}
 
-[testenv:black]
+[testenv:format]
+description = Runs the formatter (just showing errors by default)
+labels = check
 package = skip
 deps = ruff
 commands = ruff format {posargs:--diff}
 
 [testenv:typecheck]
+labels = check
 package = skip
 deps =
      mypy
      types-PyYaml
      ./ua-parser-builtins
-commands = mypy {posargs:}
+commands = mypy {posargs}
+
+[testenv:docs]
+description = Builds the documentation
+labels =
+package = skip
+deps = sphinx
+commands = sphinx-build -M {posargs:html} doc docs/_build