fix(docs): fix typo in README align attr and Python version in CONTRIBUTING (#150)

- README.md: remove spurious space in align=" center" → align="center"
  (logo was not centered on GitHub due to invalid HTML attribute value)
- CONTRIBUTING.md: correct Python prerequisite from '>= 3.9' to '3.10 - 3.12'
  to match pyproject.toml classifiers and CI matrix (cp310, cp312)

CONTRIBUTING.md

@@ -12,7 +12,7 @@ By participating, you agree to abide by our [Code of Conduct](CODE_OF_CONDUCT.md
 ## Development Setup
 
 ### Prerequisites
-- Python ≥ 3.9
+- Python 3.10 - 3.12
 - CMake ≥ 3.26, < 4.0 (`cmake --version`)
 - A C++17-compatible compiler (e.g., `g++-11+`, `clang++`, Apple Clang on macOS)
 

README.md

@@ -1,4 +1,4 @@
-<div align=" center">
+<div align="center">
   <picture>
     <source media="(prefers-color-scheme: dark)" srcset="https://zvec.oss-cn-hongkong.aliyuncs.com/logo/github_log_2.svg" />
     <img src="https://zvec.oss-cn-hongkong.aliyuncs.com/logo/github_logo_1.svg" width="400" alt="zvec logo" />