Add docs for mixin operators #830

Job	Run time
Compute matrix	5s
Doxygen check	18s
Verify Dev Containers / Verify devcontainers	7s
CUDA12.6 gcc / amd64 / Build gcc12/C++17 / Build gcc12/C++17	3m 10s
CUDA12.6 gcc / amd64 / Build gcc13/C++17 / Build gcc13/C++17	3m 1s
CUDA11.8 gcc / amd64 / Build gcc11/C++17 / Build gcc11/C++17	2m 31s
CUDA12.6 gcc / arm64 / Build gcc12/C++17 / Build gcc12/C++17	2m 16s
Verify Dev Containers / List devcontainers	2s
Verify Dev Containers / cuda11.8-gcc11	1m 0s
Verify Dev Containers / cuda12.6-gcc12	1m 3s
Verify Dev Containers / cuda12.6-gcc13	1m 8s
Verify Dev Containers / cuda12.6-gcc13	1m 0s
CUDA12.6 gcc / arm64 / Test ${{ inputs.test_name }}	0s
CUDA11.8 gcc / amd64 / Test gcc11/C++17 / Test gcc11/C++17	5m 45s
CUDA12.6 gcc / amd64 / Test ${{ inputs.test_name }}	0s
CUDA12.6 gcc / amd64 / Test gcc12/C++17 / Test gcc12/C++17	6m 48s
CI success	1s
	28m 15s

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