docs: adding removeEventListener in examples

[danieljpgo]

Improving the documentation, adding removeEventListenerin the examples.

https://github.com/shuding/cobe/issues/77

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Name	Status	Preview	Comments	Updated (UTC)
cobe	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Jul 18, 2023 11:33pm

[shuding]

Thanks!