Create syntax for icons

[Mpdreamz]

Today icons are referenced manually e.g:

:: warn: Documentation.Builder.Log[0] External URI 'https://doc-icons.s3.us-east-2.amazonaws.com/icon-no.png' is not allowed. Add 'amazonaws.com' to the 'external_hosts' list in the configuration file '/github/workspace/docset.yml' to allow links to this domain. (/github/workspace/solutions/search/cross-cluster-search.md:1122)
:: warn: Documentation.Builder.Log[0] External URI 'https://doc-icons.s3.us-east-2.amazonaws.com/icon-no.png' is not allowed. Add 'amazonaws.com' to the 'external_hosts' list in the configuration file '/github/workspace/docset.yml' to allow links to this domain. (/github/workspace/solutions/search/cross-cluster-search.md:1122)

Once we settle on a UI framework and icon pack we should make it easy to add icons through e.g :yes: and :no: inline syntax.

That way we can ensure these match the style and light/dark theme.

[reakaleek]

Tailwind's icon pack https://heroicons.com/
tabler-icons https://tablericons.com/

Just posting some icon packs that provide the svg.

We should probably use https://github.com/elastic/eui/tree/main/packages/eui/src/components/icon/svgs

[bmorelli25]

There could be value in eventually providing support for Elastic product and app logos as well.

[reakaleek]

For reference: elastic/security-docs#6555 is an example use case for this.