Better error message when node.exe isn't in path

[bterlson]

Sometimes, for reasons, node.exe may not be in a users path. There should be a better error message.

Additionally, allowing users to configure an explicit node path so that they don't need node.exe in their environment would probably be welcome in exotic situations.

[timotheeguerin]

Is there not a way to use vscode node.exe?

[nguerrera]

There is a way. We stopped using it because at one point VS Code node was too old for us.

[nguerrera]

The way is to pass a NodeModule instead of an Executable to the LanguageClient constructor in extension.ts.

[mzhongl524]

Can provide better error message , verified