docs: link LF Energy landing page

[VITA2aishu]

Adds the LF Energy Power Grid Model project-page link to the documentation landing page. Addresses the corresponding repository item in PowerGridModel/power-grid-model#1020.

[nitbharambe]

Hi @VITA2aishu , I see a DCO signoff and Commit signing is missing on a commit. You can find how to do so in https://power-grid-model.readthedocs.io/en/stable/contribution/CONTRIBUTING.html

You can first set up Commit signing via any of the methods mentioned in : https://docs.github.com/en/authentication/managing-commit-signature-verification/signing-commits
You can confirm via a `Verified tag next to a signed commit within the PR.

You can add it retroactively for DCO: https://github.com/PowerGridModel/power-grid-model-io/pull/486/checks?check_run_id=99700385518

However since both are missing, its easier if you force push a Signed and signed off commit. Hence via git commit -S -sm "commit message".

I shall review again after passing checks