Put the setLanguageConfiguration code in the appropriate place

Currently main.ts is mostly populated with this mystifying code blob:
https://github.com/PowerShell/vscode-powershell/blob/6c96a2d56b9593a25e6960df2c6f3767b3d30177/src/main.ts#L53-L104

It seems to have some PowerShell related bits in it, but also some JS doc comment stuff...

It probably shouldn't be in main.ts, and we should work out if it even causes anything. I suspect it's getting ignored in favour of the code in https://github.com/Microsoft/vscode/blob/master/extensions/powershell/language-configuration.json.

We should investigate and:

• if the code here is being preferred, move it to a more sensible location in the repo and make sure it's up to do
• if the VSCode JSON is being preferred, delete this code

Start with the setLanguageConfiguration code in src/main.ts at the linked lines, then compare it with the VS Code language-configuration.json referenced in the issue. Determine which configuration is used and whether the TypeScript code has an effect. Done means either moving and updating the code in a more suitable location, or removing it if the JSON is preferred.