Move contributing.md - #481

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: hendrikmuhs/ccache-action@v1.2. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

`auto-activate-base` is deprecated. Please use `auto-activate`. If your installer does not use the `base` environment as the default environment, also add `activate-environment: base`.

'nodefaults' channel detected: will remove 'defaults' if added implicitly. In the future, 'nodefaults' to remove 'defaults' won't be supported. Please set 'conda-remove-defaults' = 'true' in setup-miniconda to remove this warning.

`auto-activate-base` is deprecated. Please use `auto-activate`. If your installer does not use the `base` environment as the default environment, also add `activate-environment: base`.