Add *.csproj.lscache to .gitignore to prevent files from being tracked

[liamjpeters]

PR Summary

The C# Dev Kit for VS Code now puts .csproj.lscache files next to each .csproj file. They contain project structure and metadata info, and allow C# Dev Kit to skip expensive work at startup.

The files themselves state It can safely be deleted and will be regenerated automatically..

PR adds them to gitignore.

See https://aka.ms/lscache for more info.

PR Checklist

• PR has a meaningful title
  • Use the present tense and imperative mood when describing your changes
• Summarized changes
• Change is not breaking
• Make sure all .cs, .ps1 and .psm1 files have the correct copyright header
• Make sure you've added a new test if existing tests do not effectively test the code changed and/or updated documentation
• This PR is ready to merge and is not Work in Progress.
  • If the PR is work in progress, please add the prefix WIP: to the beginning of the title and remove the prefix when the PR is ready.

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[andyleejordan]

It's bonkers to me that they're suggesting cache data be committed to version control 😬 also can set dotnet.projectsystem.cacheInProjectFolder to false. Perhaps we should do that in the workspace instead?

[andyleejordan]

They've admitted that it was an accidental rollout to release that that setting isn't defaulting to false.