chore: Bump package version to 0.3.0 (#87)

Co-authored-by: 99 <wh2099@pm.me>

Author: laipz8200

pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = 'graphon'
-version = "0.2.2"
+version = "0.3.0"
 description = 'Graph execution engine for agentic AI workflows.'
 readme = 'README.md'
 license = 'Apache-2.0'