Stack trace URL improvements

[fonsp]

New features:

• Clickable URLs for functions from packages (thanks to @adrhill !!)
• Show package name for external functions
• Icon to show that the link will open in a new tab
• Some CSS tweaks

Example

Example

[github-actions]

Try this Pull Request!

Open Julia and type:

julia> import Pkg
julia> Pkg.activate(temp=true)
julia> Pkg.add(url="https://github.com/fonsp/Pluto.jl", rev="stack-frame-url-imrpvoements")
julia> using Pluto

[fonsp]

The new URL code does not work on Julia 1.6, and I don't see an easy way to make it work :(

[fonsp]

It might be worth trying this code JuliaLang/julia#47709 (comment) ? RegistryInstances might be okay to add as a dep

[cstjean]

The clickable URL feature is what I'm talking about in #2737 (comment). I would selfishly prefer JULIA_EDITOR over an URL because

• It works even if offline
• It works for local packages
• It's always pointing to the right line, even for old versions.
• My editor is comfier than github.

I know you favor simplicity and what's-best-for-students, so I'm not going to get my hopes up. This PR as is looks great!