feat: add a CodeQL workflow

[bobbyxng]

The repo's branch ruleset requires code scanning results before merging, but the workflow has not produced any yet. Standard GitHub-generated setup, scoped to this repo's primary language (Python).

Reviewer checklist

• There are no pip dependencies in the module's environment files (workflow/envs/).
• All rules use pathvars (e.g., <results>) in their inputs and outputs.
• The integration test-suite is successful, including:
  • pre-commit.ci tests pass.
  • tests pass for all relevant OS configurations (linux, osx, windows).
• Module documentation is up-to-date, including:
  • INTERFACE.yaml mentions all relevant pathvars and wildcards.
  • README.md describes how to use the module and has the necessary citations.

[github-advanced-security]

You are seeing this message because GitHub Code Scanning has recently been set up for this repository, or this pull request contains the workflow file for the Code Scanning tool.

What Enabling Code Scanning Means:

• The 'Security' tab will display more code scanning analysis results (e.g., for the default branch).
• Depending on your configuration and choice of analysis tool, future pull requests will be annotated with code scanning analysis results.
• You will be able to see the analysis results for the pull request's branch on this overview once the scans have completed and the checks have passed.

For more information about GitHub Code Scanning, check out the documentation.