[MISC] Improve metadata

[astrojuanlu]

So that there's a link to this repository from https://pypi.org/project/object-storage-charmlib/ and the README is used as full description.

Refs:

• https://packaging.python.org/en/latest/specifications/pyproject-toml/#urls
• https://packaging.python.org/en/latest/specifications/well-known-project-urls/#well-known-labels

--- object_storage_charmlib-0.1.0.dist-info_OLD/METADATA        2016-01-01 00:00:00.000000000 +0100                                                                                                                                                                                                                                                                         
+++ object_storage_charmlib-0.1.0.dist-info/METADATA    2016-01-01 00:00:00.000000000 +0100                                                                                                                                                                                                                                                                                 @@ -12,3 +12,437 @@                                                      
 Classifier: Programming Language :: Python :: 3.13                                                                                                                                   
 Classifier: Programming Language :: Python :: 3.14                                                                                                                                                                                                                                                                                                                         
 Requires-Dist: ops (>=2.0.0)                                                                                                                                                                                                                                                                                                                                               
+Project-URL: source, https://github.com/canonical/object-storage-integrator/tree/main/lib                                                                                                                                                                                                                                                                                  
+Description-Content-Type: text/markdown                                                                                                                                              
+                                                                  
+# Object Storage Charmlib                                                                                                                                                                                                                                                                                                                                                  
+                                                                                                                                                                                                                                                                                                                                                                           
+[![PyPI](https://img.shields.io/pypi/v/object-storage-charmlib)](https://pypi.python.org/pypi/object-storage-charmlib)                                                                                                                                                                                                                                                     
+                                                                                                                                                                                                                                                                                                                                                                           
+The `object-storage-charmlib` is a Python charm interface library for ...

[astrojuanlu]

Preview: https://test.pypi.org/project/object-storage-charmlib/0.1.0.dev120714395216/