rust

Add 'WIT by Example' section #183

Job	Run time
build (component-model/examples/tutorial/adder, component)	26s
build (component-model/examples/tutorial/command, component)	23s
build (component-model/examples/tutorial/calculator, component)	24s
build (component-model/examples/example-host)	2m 2s
	3m 15s

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