docs: highlight CI Git environment configuration instruction

[babblebey]

This pull request updates the README.md to clarify the responsibilities of composed callers (such as wrapper packages or direct invocations) regarding Git environment configuration in CI environments. It highlights that @semantic-release/core does not set Git defaults for composed callers, and provides explicit guidance and code examples to prevent common CI failures related to Git author identity and credential prompts.

Documentation improvements for CI and Git environment configuration:

• Added a clear explanation that composed callers must configure the Git process environment (e.g., GIT_AUTHOR_NAME, GIT_COMMITTER_NAME, GIT_ASKPASS, GIT_TERMINAL_PROMPT) before invoking @semantic-release/core, as core does not inject these defaults for them. [1] [2]
• Provided a typical CI setup code example showing how to set the necessary Git environment variables to avoid failures during publishing in non-interactive environments. [1] [2]
• Updated documentation to emphasize that wrapper/caller code owns Git process environment hardening and should set these variables before invoking core.

[github-actions]

🎉 This PR is included in version 1.0.0-beta.2 🎉

The release is available on:

• npm package (@beta dist-tag)
• GitHub release

Your semantic-release bot 📦🚀