fix optional dependency, bump version

Signed-off-by: Zen <[email protected]>

Author: desultory

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "pycpio"
-version = "1.5.0"
+version = "1.5.1"
 
 authors = [
   { name="Desultory", email="[email protected]" },
@@ -17,7 +17,10 @@ classifiers = [
     "License :: OSI Approved :: GNU General Public License v2 (GPLv2)",
     "Operating System :: OS Independent",
 ]
-dependencies = ["zenlib >= 3.0.2", "zstd >= 1.5.6.1"]
+dependencies = ["zenlib >= 3.0.2"]
+
+[project.optional-dependencies]
+zstd = ["zstd >= 1.5.6.1"]
 
 [project.scripts]
 pycpio = "pycpio.main:main"