Update poetry dependency groups to allow having pillow and png together

Author: maribedran

pyproject.toml

@@ -48,12 +48,15 @@ pillow = {version = ">=9.1.0", optional = true}
 [tool.poetry.extras]
 pil = ["pillow"]
 png = ["pypng"]
+all = ["pypng","pillow"]
 
 [tool.poetry.group.dev.dependencies]
 pytest = {version = "*"}
 pytest-cov = {version = "*"}
 tox = {version = "*"}
 ruff = {version = "*"}
+pypng = {version = "*"}
+pillow = {version = ">=9.1.0"}
 docutils = "^0.21.2"
 zest-releaser = {extras = ["recommended"], version = "^9.2.0"}