docs: Deprecating message for problem-builder (#420)

This change adds a message deprecating problem builder.

Announcement on forums: https://discuss.openedx.org/t/deprecation-removal-problem-builder-repository/13664
DEPR Ticket: openedx/public-engineering#268

Author: xitij2000

README.md

@@ -1,3 +1,10 @@
+> [!WARNING]
+> Problem Builder is no longer being developed by OpenCraft.
+> It will be supported with compatibility and security fixes
+> till the Ulmo release, after which this repository will be
+> stop receiving further updates and eventually be archived.
+
+
 ## Problem Builder and Step Builder
 
 [![Circle CI](https://circleci.com/gh/open-craft/problem-builder.svg?style=svg)](https://circleci.com/gh/open-craft/problem-builder)

problem_builder/__init__.py

@@ -1 +1 @@
-__version__ = "5.2.0"
+__version__ = "5.2.1"

setup.py

@@ -167,7 +167,13 @@ def package_data(pkg, roots):
 setup(
     name='xblock-problem-builder',
     version=VERSION,
-    description='XBlock - Problem Builder',
+    description='XBlock - Problem Builder [deprecated]',
+    classifiers=[
+        "Development Status :: 7 - Inactive",
+        "Programming Language :: Python :: 3",
+        "Programming Language :: Python :: 3.11",
+        "Programming Language :: Python :: 3.12",
+    ],
     long_description=README,
     long_description_content_type='text/markdown',
     author='OpenCraft',