Add Hugo Pipes logic for local and vendored scripts.

Created by: regisphilibert

@XhmikosR

I stored the Hugo pipe logic in a returning partial so we can:

1. not concern ourselves with whitespace and line breaks when working logics
2. use partialCached on the logic
3. compontentize.

Also:

• When missing mounts, I'm using warnings instead of errors, but I think you wanted errors so the build is stopped. In this case we can replace warnf by errorf through the code.
• For now the docsearch.min.js file is not published at the desired permalink (including version) but will after Hugo .74 introduces the new resources.Put method (see comment)
• I'm not 100% sure the order in which files should be bundled is correct, but I don't have any errors in console.
• I used my own conventions for file naming and commenting, feel free to adjust to the team's own.
• I left alone the asset loaded from CDN (bootstrap.bundle.min.js), but once you are ready to let Hugo handle it we'll just have to include in the GetJSAssets partial.

Preview: https://deploy-preview-29283--twbs-bootstrap.netlify.app/