Add comprehensive codec management functionality (#24)

* Add comprehensive codec management functionality

* Address minor PR review recommendations

- Add Code Management section to README with usage examples
- Add return type annotation to load_codecs_from_file()
- Improve newsfragment formatting (remove backticks)

* Fix ReST title underline length in README

---------

Co-authored-by: acul71 <[email protected]>

Author: sumanjeet0012

README.rst

@@ -53,6 +53,33 @@ Sample Usage
     >>> get_codec(b'\x12EiC5TSe5k00')
     'sha2-256'
 
+Code Management
+===============
+
+In addition to the basic prefix operations, py-multicodec provides type-safe codec
+management functionality:
+
+.. code-block:: python
+
+    >>> from multicodec import Code, known_codes
+    >>> from multicodec.code_table import SHA2_256, DAG_CBOR
+
+    >>> # Use named constants for type-safe codec handling
+    >>> code = SHA2_256
+    >>> str(code)
+    'sha2-256'
+    >>> int(code)
+    18
+
+    >>> # Create Code from string (name or hex)
+    >>> code = Code.from_string("sha2-256")
+    >>> code = Code.from_string("0x12")  # hex also works
+
+    >>> # List all known codecs
+    >>> all_codes = known_codes()
+    >>> len(all_codes)
+    460
+
 Updating the lookup table
 ==========================
 

multicodec/__init__.py

@@ -4,13 +4,32 @@
 __email__ = "[email protected]"
 __version__ = "0.2.1"
 
+# Core Code type
+from .code import (
+    RESERVED_END,
+    RESERVED_START,
+    Code,
+    is_reserved,
+    known_codes,
+)
+
+# Original multicodec functions
 from .multicodec import add_prefix, extract_prefix, get_codec, get_prefix, is_codec, remove_prefix
 
 __all__ = [
+    "RESERVED_END",
+    # Constants
+    "RESERVED_START",
+    # Code type
+    "Code",
+    # Original functions
     "add_prefix",
     "extract_prefix",
     "get_codec",
     "get_prefix",
     "is_codec",
+    "is_reserved",
+    # Functions
+    "known_codes",
     "remove_prefix",
 ]