Add basic page for troubleshooting app launch failures

[elinor-fung]

Summary

Add basic page for troubleshooting app launch failures.

This is very basic/sparse right now - just trying to get a basic landing page so the end-user-facing framework resolution failure link (https://aka.ms/dotnet/app-launch-failed) we are adding in dotnet/runtime#67022 has something it can redirect to.

cc @richlander @vitek-karas

[vitek-karas]

@richlander - not sure if we want to promote extracting zips as an install experience. Maybe this should point to some overall "how to install" page just noting the typical difference between default location (should use installers/packages) and non-default location in which case I would recommend usage of the dotnet-install script.

[elinor-fung]

I felt like the dotnet-install scripts would be less end-user-friendly? I knew how to download and extract before doing any software development, but I didn't know how to run anything in PowerShell or bash.

[vitek-karas]

I kind of agree - but to a point. I think the general problem with the current web-site/download/install experience as driven by the host is that we don't point to a specific single download - the user still has to choose (click on the right option on the web-site).

The experience for the installers is reasonable in that the web-site has nice, large pictures and text and so on, and it takes like 1-2 clicks to get the thing (assuming you know what - which is another problem).

Downloading the zips is worse - you have to go through the a "All downloads" page which is overwhelming even for me. In that sense, asking the user to run something like dotnet-install.ps1 --version 1.2.3 --framework ASP.NET --location C:\private feels much simpler and also feels much more in-line with the CLI experience which is probably the preferred way for devs anyway. And it's fully scriptable/repeatable (as in - oh I need new SDK for this thing, OK, now it works locally, but what do I add to my CI to make it work there).

But I agree that this is a much larger discussions and should not block these changes in any way.

[elinor-fung]

That's definitely fair. 'All downloads' does have a lot going on and the user needs to map the information in the error message to multiple separate actions/clicks, while the script can just take all the information in a single command.

I'm going to put this in its current state so that we at least have a page. I'll likely add a section pointing at the script later. (And I'm sure we will need some iteration / improvement after.)