Re-enable Blazor linting

[msmithNI]

Pull Request

🤨 Rationale

#1280

👩‍💻 Implementation

It looks like a the build agent began pulling in a new version of the .NET tools. dotnet --info prints out this for the CI build:

.NET SDKs installed:
  6.0.408 [/usr/share/dotnet/sdk]
  7.0.105 [/usr/share/dotnet/sdk]
  7.0.203 [/usr/share/dotnet/sdk]
  7.0.302 [/usr/share/dotnet/sdk]

So I'm guessing that 7.0.302 is causing issues.

I found dotnet/format#1800 which is pretty close to what we're seeing. This comment makes it sound like there'll be a newer 7.0.3xx version that will fix this problem, but the issue is still open so I guess that version isn't out yet.
Also see dotnet/format#1834 and dotnet/sdk#32598 which reference 7.0.302 and the DLL v4.6.0.0 specifically.

Changes in this PR:

• Re-enable Blazor C# linting in package.json
• Add a global.json file to ensure the dotnet commands are using .NET 6.0.xxx tooling.
  • This will ensure both the CI and local builds are using the .NET 6 SDK for the dotnet CLI commands
• Add a pipeline step to print out dotnet --info, which will print out all the installed .NET SDK versions, which should make it easier to debug issues like this in the future
• Update docs to explicitly call out that a .NET SDK install 6.0.202 <= v < 7 is required
• Update the CI build (main.yml) setup-dotnet action to refer to global.json to get the required .NET version to install (so we're not encoding the required version in multiple places in code)

🧪 Testing

CI build + re-built locally.

✅ Checklist

• I have updated the project documentation to reflect my changes or determined no changes are needed.