feat: add EnviromentKeyMissing exception for missing environment variables

README.md

@@ -107,3 +107,8 @@ All built-in cast functions handle common edge cases:
 | `cast_none_or_str` | Returns `None` if value is `null` or `None` |
 
 ---
+
+### EnviromentKeyMissing
+
+if a key is get from `env.get` and it has no default given it will raise
+EnviromentKeyMissing(f"Environment variable '{key}' not found.")

setup.py

@@ -2,7 +2,7 @@ from setuptools import setup, find_packages
 
 setup(
     name='multinut',
-    version='0.2.2',
+    version='0.2.3',
     packages=find_packages(),
     install_requires=["dotenv"],
     author='Chipperfluff',