Allow developers to skip the build of the examples

[jorgepiloto]

Every time the documentation of this project is built, various requests get performed to fetch third party examples.

Multiple runs lead to these third parties blocking for 5 min any additional requests.

We should allow to skip the build of the examples via the Jinja approach we have in other projects.

Note

Before contributing and starting any work, please make sure you agree with the CLA and sign it in your PR.

[Revathyvenugopal162]

Steps to Implement:

• Ensure that sphinx_jinja is included as a dependency in pyproject.toml (it is already present).
• Implement Build Example Environment Variable: https://github.com/ansys/pyansys-geometry/blob/main/doc/source/conf.py#L353
• Update examples.rst: https://github.com/ansys/pyansys-geometry/blob/main/doc/source/index.rst?plain=1#L41

Acceptance Criteria:

• - The build process can successfully skip examples based on the environment variable.
• - The Jinja template is properly integrated and functioning in index.rst.
• - All changes are tested, and documentation is updated accordingly.