Add `image_math` tool #270

Job	Run time
Setup cache and determine changed repositories (3.11)	46s
Lint R scripts (ubuntu-20.04, release)	1m 41s
Check file sizes	8s
Lint Python scripts (3.11)	14s
Lint tool-list (3.11)	33s
Test tools (0, 3.11)	6m 45s
Combine chunked test results (3.11)	44s
Check workflow success	1s
Deploy	0s
Report deploy status	0s
	10m 52s

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