Preview failed on Windows 7/10

[anieriz]

Hi !
I am getting a error when trying to preview a file that have blank spaces in the name or blank spaces in the directory path.

[lextm]

The cause is that fileName is not quoted,

https://github.com/tht13/RST-vscode/blob/master/src/rstEngine.ts#L20

Try to avoid spaces in file names before the author fixes the code.