Support for Ubuntu 26.04

[hugovk]

GitHub will start moving ubuntu-latest to Ubuntu 26.04 next month:

Breaking changes

The ubuntu-latest label is ready to become the default version for Ubuntu 26.04.

Target date

This change will be rolled out over a period of several weeks beginning October 19, 2026.
We plan to complete the migration by November 19, 2026.

actions/runner-images#14748

[GuillaumeLagrange]

Thanks for the heads up, we'll add support for ubuntu 26 before github rolls it out!