Added functionality for callbacks #491

Job	Run time
semver	51s
Clippy	3m 3s
Code Coverage	7s
Build Examples (3d_charts)	57s
Build Examples (basic_charts)	37s
Rustfmt	11s
Build Wasm Examples (wasm-yew-minimal)	49s
Build Examples (custom_controls)	22s
Tests (ubuntu-latest)	2m 19s
Build Examples (financial_charts)	29s
Tests (windows-latest)	4m 29s
Build Examples (images)	41s
Tests (macos-latest)	2m 38s
Build Examples (kaleido)	1m 32s
Build Examples (maps)	23s
Build Examples (ndarray)	33s
Build Examples (scientific_charts)	22s
Build Examples (shapes)	28s
Build Examples (subplots)	21s
	21m 12s

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