Automate chat template JS dependency updates

Following are the main changes in this PR:

1. Add apackage.json to specify project template dependencies and how they should be copied into template content
   • Note that this is only a development-time dependency and doesn't ship with the templates. That is, we're not adding back a dependency on NPM for the shipping templates.
2. Add acopyDependency.mjs script that carries out the actual dependency copying.
   • It also updates the package version in the README file
3. Reduce the number of assets required for PDF viewing (more info below).

PDF viewer changes

Thepdfjs dependency was trickier than the others, because its NPM package (pdfjs-dist) doesnot include the built-in PDF viewer that was being utilized by the chat template. There are numerous issues in the pdf.js GitHub repo asking for the viewer to be included, but the maintainers havestated that they don't want people to use the PDF viewer "as-is" in actual code:

The viewer is built on the display layer and is the UI for the PDF viewer in Firefox and the other browser extensions within the project. It can be a good starting point for building your own viewer.However, we do ask if you plan to embed the viewer in your own site, that it not just be an unmodified version. Please re-skin it or build upon it.

Given this statement and the fact that it was intentionally made difficult to use the built-in PDF viewer, it's probably best to find an alternative.

Thankfully, it's pretty straightforward to recreate a super minimal PDF viewer using pdf.js directly. I've added two assets to thewwwroot folder in the template that define a custom viewer:

• pdf_viewer.html
• pdf_viewer.js

These assets won't get updated automatically, but they probably won't need to be anyway unless there's a significant breaking change in pdf.js.

It's pretty minimal, but I don't think we need anything more advanced for a template:

One advantage to this is that we can significantly reduce the number of assets required for PDF viewing (all the images except for the loading icon can be removed).

In the future, we could even replacepdf_viewer.html with a Blazor component that displays the citation in a modal dialog. But I'm hoping we would address that in a follow-up.

Future work

This PR does not add a CI pipeline to update template dependencies. It's still "manual" in that you have to clone the repo and run these two commands from thesrc/ProjectTemplates folder:

npm installnpm run copy-dependencies

However, this is how it works in the ASP.NET Core repo as well, and I'd imagine it saves about 90% of the effort required to update dependencies.

This PR also doesn't do anything to automate .NET dependency updates. If we think this would be helpful, I'll address it in a follow-up PR to keep this one focused.

Fixeshttps://github.com/dotnet/ai-private-planning/issues/276

Microsoft Reviewers:Open in CodeFlow