📚🩹 Fix broken demos in the docs are broken due to 404 error fetching cytoscape.min.js

[s-weigand]

Associated issues:

• 📚🐛 Some demos in the docs are broken due to 404 error fetching cytoscape.min.js #3259
• Many of the demo networks are broken #3257

Notes re. the content of the pull request. Give context to reviewers or serve as a general record of the changes made. Add a screenshot or video to demonstrate your new feature, if possible.

• This PR fixes that cytoscape.min.js gets copied into documentation/js/build instead of documentation/js due to a breaking change in cpy-cli>=4.0.0 introduced by Build(deps): Bump braces and cpy-cli #3247

Remove the --parents flag. The copy is now recursive by default. To get flat output, use the --flat flag.

• This PR replaced the polyfill.io cdn links with the corresponding cloudflare cdn links since polyfill.io is a known potential security risk.
• This PR replaces the broken external link to the cytoscape.js-cise demo with the working one
• This PR adds cytoscape.min.js in docs folder to .gitignore so it won't be accidentally committed.
  This also simplifies pruning by using git clean -dfX (will remove all gitignored files and folders)

Checklist

Author:

• The proper base branch has been selected. New features go on unstable. Bug-fix patches can go on either unstable or master.
• N/A -- Automated tests have been included in this pull request, if possible, for the new feature(s) or bug fix. Check this box if tests are not pragmatically possible (e.g. rendering features could include screenshots or videos instead of automated tests).
• The associated GitHub issues are included (above).
• Notes have been included (above).

Reviewers:

• All automated checks are passing (green check next to latest commit).
• At least one reviewer has signed off on the pull request.
• For bug fixes: Just after this pull request is merged, it should be applied to both the master branch and the unstable branch. Normally, this just requires cherry-picking the corresponding merge commit from master to unstable -- or vice versa.

closes #3259
closes #3257

[maxkfranz]

Looks good but I'd revert the gitignore

[maxkfranz]

👍 LGTM

[maxkfranz]

Merged and cherry-picked to unstable branch. Thanks @s-weigand . Great PR