Update README branding and add example usage demo - #41

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/cache@v4, conda-incubator/setup-miniconda@v3. 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`.

WARNING conda.models.version:get_matcher(564): Using .* with relational operator is superfluous and deprecated and will be removed in a future version of conda. Your spec was 2.12.*, but conda is ignoring the .* and treating it as 2.12

The 'defaults' channel might have been added implicitly. If this is intentional, add 'defaults' to the 'channels' list. Otherwise, consider setting 'conda-remove-defaults' to 'true'.