add file formats tag

pyproject.toml

@@ -44,6 +44,7 @@ classifiers = [
     "Intended Audience :: Science/Research",
     "License :: OSI Approved :: GNU General Public License v3 (GPLv3)",
     "Topic :: Scientific/Engineering :: Electronic Design Automation (EDA)",
+    "Topic :: File Formats",
     ]
 requires-python = ">=3.11"
 include = [
@@ -54,6 +55,11 @@ dependencies = [
     "numpy>=1.26",
     ]
 
+[build-system]
+requires = ["hatchling"]
+build-backend = "hatchling.build"
+
+
 [tool.hatch.version]
 path = "klamath/__init__.py"