Add notebook for computing WFM time-of-flight #324

Job	Run time
Formatting and static analysis	17s
Mantid tests	5m 21s
Tests (ubuntu-22.04, 3.10, py310) / package-test	21s
Tests (ubuntu-22.04, 3.10, py310) / test	1m 18s
docs / Build documentation	3m 30s
	10m 47s

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