docs: add Sass deprecations notice in docs

[MaxLardenois]

Description

This PR will add a callout in the docs to explain and provide links to potential resolution regarding Sass depreciation. Also it modifies Vite, Parcel and Webpack configs to silence the deprecations warnings from Dart Sass.

Motivation & Context

Many issues are opened regarding the Sass deprecation notices (see #40962) and users must search the web to pinpoint the problem and potential workarounds, adding a callout directly in the docs while the core team is working on node Sass exit would be helpful for users and would limit erroneous new issues opening about these deprecations.
We have the same problems with our company's fork's users who must search the web for information about these issues but we figured it could be an improvement on Bootstrap docs directly.

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-41283--twbs-bootstrap.netlify.app/docs/5.3/customize/sass/
• https://deploy-preview-41283--twbs-bootstrap.netlify.app/docs/5.3/getting-started/webpack/
• https://deploy-preview-41283--twbs-bootstrap.netlify.app/docs/5.3/getting-started/vite/

Related issues

#40962

[julien-deramond]

Thanks for this PR, @MaxLardenois!
I haven’t reviewed the exact wording and modifications in detail, but I’m not opposed to adding it temporarily to our documentation. However, we need to carefully coordinate the merge of this PR with our upcoming releases.
If we want this change to be useful in time, it should be included in v5.3.4. Additionally, if this is merged, we’ll need to update twbs/examples accordingly.
@mdo, what do you think? Should I help move this PR forward?

[mdo]

Some edits that I'll accept after posting this.

[julien-deramond]

Thanks again for the PR! I fixed the cspell error, aligned the new comments for consistency, and adjusted the step in the Parcel guide so that the file is added only when needed. For the other two guides, they’re easier to explain once the config is in place.

Once this PR is merged, I’ll:

• open a PR in twbs/examples to apply these changes
• update my "Drop Node Sass" PR to consider removing these changes from both the documentation and twbs/examples