Automatically continue doc comments

[unleashy]

Fixes #407.

The rules were just taken and adjusted from https://github.com/PowerShell/vscode-powershell/blob/43c8bff8bd316684fb4bc82cdbed36ceb7988904/src/extension.ts#L80-L114.

///-comments are not included but could easily be added in if needed:

{
	"beforeText": "^\\s*\\/\\/\\/\\s*[^\\s]+$",
	"action": { "indent": "none", "appendText": "/// " }
}