Upgrade dependencies

[tylervz]

This pull request upgrades several Node dependencies of the extension.

I removed vscode from package.json and ran npm i -D @types/vscode and npm i -D vscode-test @vscode/test-cli @vscode/test-electron because the vscode package has been replaced by those.

And then I updated the VSCode config files to match those of a new extension generated with npx --package yo --package generator-code -- yo code as described in the documentation. This involved updating the package.json scripts to copy the language-configuration folder to out after compilation and updating the paths in src/configuration.ts because the rootDir changed from "." to "src" in tsconfig.json.

It seems that upgrading the dependencies of this extension has fixed this bug (#47). It launches fine from VS Code when the ..../src/xaml/language-configuration.json file on my computer has a trailing comma in the onEnterRules array. But if I remove the opening square bracket of the onEnterRules array, then this extension reports problems when I try to launch it.