Add the location information for the execution of child process

[44ka28ta]

When pandoc executes as the child process, the execution location is obscure. So, PDF generation fails in my environment. this error log shown in the console of the developer tool is as follows:

[Plugin Host] exec error: Error: Command failed: C:\WINDOWS\system32\cmd.exe /s /c
"pandoc "c:\Users\hata\Documents\sample.md" -o "c:\Users\hata\Documents\sample.pdf"
--latex-engine=xelatex -V documentclass=bxjsarticle -V geometry:a4paper -V classoption:pandoc -V classoption:jafont=yu-win"
pandoc: CreateDirectory ".\\tex2pdf.7496": permission denied

Probably, the child process of pandoc executes in a system directory.
For this reason, I modified the code for to specify the execution path of the child process and PDF generation succeeded.

[satokaz]

@dfinke, There are users who have the same problem.

Current directory when code.exe process was started further is set to cwd of code.exe.
Will fail if no write access to the set cwd.

adding {cwd filePath}, cwd of the called exec process is set to filePath.
I believe that it is possible to avoid the problem in this fix.

Could you merge the PR?

[dfinke]

Thanks for the PR. Let me review and test. I may not be able to get to this for a couple of days