Release v1.5

[RaulPPelaez]

Several features have been included since the last release (last year), should we make a new one?

What's Changed

• Can compute parameter derivatives by @peastman in https://github.com/openmm/openmm-torch/pull/143
• Attempts at fixing CI by @peastman in https://github.com/openmm/openmm-torch/pull/144
• Freeze pytorch model by @peastman in https://github.com/openmm/openmm-torch/pull/148
• Add energy derivatives to README by @RaulPPelaez in https://github.com/openmm/openmm-torch/pull/145
• Serialize property values by @peastman in https://github.com/openmm/openmm-torch/pull/152
• Update Mac build to newer versions by @peastman in https://github.com/openmm/openmm-torch/pull/153

@peastman is there anything you would like to add in before v1.5?