Docs for the 0.21 release

[anna-geller]

Don't merge before 4th of Feb

[cloudflare-workers-and-pages]

Deploying kestra-io with    Cloudflare Pages

Latest commit:	b29785e
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Preview URL:	https://d96792bf.kestra-io.pages.dev
Branch Preview URL:	https://docs-release-0-21.kestra-io.pages.dev

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[aj-emerich]

Screenshot update in Alerting & Monitoring doc per Plugin Update

[wrussell1999]

finally workflow component video ready to go when there's a place for it:

<div class="video-container">
    <iframe src="https://www.youtube.com/embed/os9_WY4-9o8?si=cB0c1HksxZtDQ5GB" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share" referrerpolicy="strict-origin-when-cross-origin" allowfullscreen></iframe>
</div>

[aj-emerich]

I have added a first draft of the finally component page with Will's example from the video. Can link to more complex example blueprints when we have them 👍