docs: Fix multiple docfx, css, js, mermaid layout related issues

[agneszitte]

GitHub Issue (If applicable): Resolves #8431, Resolves #14358, Resolves unoplatform/uno-private#453, Resolves #16100

PR Type

What kind of change does this PR introduce?

• Bugfix

Description

Fix multiple docfx, css, js, mermaid layout related issues:

• Fix multiple layout/margin issues related to code snippet blocks inside tabs and lists
• Fix language display and easy-copy-paste for code snippet blocks for some pages
• Fix multiple markdown content alignments (wrong indentation for some list details for example)
• Removing <iframe /> for the youtube videos and use proper markdown [!video link] instead
• Fix mermaid massive whitespace above and below graphs with a workaround because Massive whitespace above and below graph mermaid-js/mermaid#1984 is still not fixed for the latest mermaid versions.
• Align code snippet blocks syntax to match the proper markdown syntax: ```language
  cf.
  • dotnet.github.io/docfx/docs/markdown.html?tabs=linux%2Cdotnet#mermaid-diagrams
  • dotnet.github.io/docfx/docs/markdown.html?tabs=linux%2Cdotnet#plantuml-diagrams
  • learn.microsoft.com/en-us/contribute/content/code-in-docs

Before/After

Before	After

---

Before

<div style="position: relative; width: 100%; padding-bottom: 56.25%;">
    <iframe
        src="https://www.youtube-nocookie.com/embed/BQdj9rqLcos"
        title="YouTube video player"
        frameborder="0"
        allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share"
        allowfullscreen
        style="position: absolute; top: 0; left: 0; width: 100%; height: 100%;">
    </iframe>
</div> 

After
> [!Video https://www.youtube-nocookie.com/embed/BQdj9rqLcos]

---

Before

	``` csharp
	... code snippet
	```

After

	```csharp
	... code snippet
	```

PR Checklist

Please check if your PR fulfills the following requirements:

• Docs have been added/updated which fit documentation template (for bug fixes / features)
• Unit Tests and/or UI Tests for the changes have been added (for bug fixes / features) (if applicable)
• Validated PR Screenshots Compare Test Run results.
• Contains NO breaking changes
• Associated with an issue (GitHub or internal) and uses the automatic close keywords.
• Commits must be following the Conventional Commits specification.

[unodevops]

🤖 Your Docs stage site is ready! Visit it here: https://unodocsprstaging.z13.web.core.windows.net/pr-16972/index.html

[agneszitte]

@Mergifyio backport release/stable/5.2

[mergify]

backport release/stable/5.2

✅ Backports have been created

• #16988 docs: Fix multiple docfx, css, js, mermaid layout related issues (backport #16972) has been created for branch release/stable/5.2

[morning4coffe-dev]

Otherwise, going thought the pages, I don't see any issues and great job with making the Video markdown syntax work!

[unodevops]

🤖 Your Docs stage site is ready! Visit it here: https://unodocsprstaging.z13.web.core.windows.net/pr-16972/index.html