[OUDS] Docs(helpers): add 'Stacks' page

[julien-deramond]

Related issues

Listed in #2589.

Description

This PR adds the "Helpers > Stacks" page based on:

• the previous corresponding Boosted page (see code source)
• the corresponding Bootstrap page (see code source)

To add to #2589

• Uncomment elements whenever /helpers/vertical-rule is added
• Uncomment elements whenever buttons are developed
• Uncomment elements whenever inputs are developed

Types of change

• New documentation (non-breaking change which adds functionality)

Live previews

• https://deploy-preview-2681--boosted.netlify.app/docs/0.0/helpers/stacks

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[louismaximepiton]

I'm fine with the following but I was wondering if the comments should be changed to follow Bootstrap or Boosted version or a ready to uncomment version.