feat: Update version to 2.2.3 and improve README

- Bumps the package version to 2.2.3 in `pyproject.toml` and `src/gmssl/_version.py`.
- Refactors all code examples in `README.md` to use explicit imports instead of wildcard imports.
- Improves the readability and clarity of the code examples by adding comments, assertions, and f-strings.
- Removes lengthy and unnecessary certificate and command-line output from the `README.md` to improve readability.

Merge pull request #6 from ferstar/update-gmssl-libs-master

chore: update bundled GmSSL libraries to master