Add code of conduct #389

Job	Run time
Build Wasm Examples (wasm-yew-minimal)	48s
Clippy	3m 19s
Code Coverage	2m 17s
Build Examples (3d_charts)	28s
Build Examples (basic_charts)	32s
Rustfmt	12s
semver	1m 21s
Build Examples (custom_controls)	32s
Tests (ubuntu-latest)	1m 54s
Build Examples (financial_charts)	22s
Tests (windows-latest)	4m 31s
Build Examples (images)	40s
Tests (macos-latest)	1m 55s
Build Examples (kaleido)	1m 19s
Build Examples (maps)	22s
Build Examples (ndarray)	23s
Build Examples (scientific_charts)	28s
Build Examples (shapes)	23s
Build Examples (subplots)	26s
	22m 12s

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