Docs: Add a way to skip some doc stuff

[louismaximepiton]

Description

Add a {{ skip (.*) }}{{ /skip }} tags to our example to change the displayed code from the executed code.
I couldn't think about it using native Hugo template ({{ if }}, etc.) so I tried to reproduce as mush as possible the syntax.
It might be far from ideal but we could merge a first version and upgrade it with time and experiment.
⚠️ Remove the doc example before merging.
Once this is merged (or equivalent) I'll update all Bootstrap examples to avoid dupe code, uniformize a bit more the documentation and add Stackblitz to all those new examples..
Should it be mentioned somewhere to help contributors discovering this feature ?

Can you think about a better approach to help with this issue ?

Motivation & Context

In context of #38933.
Avoid dupe code.
Help people maintaining only one version of each example and keep the doc tidier.

Type of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Refactoring (non-breaking change)
• Breaking change (fix or feature that would change existing functionality)

Checklist

• I have read the contributing guidelines
• My code follows the code style of the project (using npm run lint)
• My change introduces changes to the documentation
• I have updated the documentation accordingly
• I have added tests to cover my changes
• All new and existing tests passed

Live previews

• https://deploy-preview-39747--twbs-bootstrap.netlify.app/docs/5.3/components/list-group/#javascript-behavior

Related issues

#38933.

[XhmikosR]

I'm not sure I like this approach, but I can't think of a better way right now, though.

The regex seems pretty complex and having to introduce all these {{rendering}} stuff seems suboptimal and messier to just duplicating the code...

[louismaximepiton]

I see your point and I totally agree with you. I'll try to think of another way in the next days.

I forgot to mention it inside the description, but it could also help on uniformization of the documentation and make all examples in the documentation tryable via Stackblitz.