Fixes tasks.json task to latest script names

[mikaelbr]

Changes from running "watch" to running "start". Also changes from watching to background as watching is deprecated in VSCode.

Should tasks.json be placed in .vscode or is it other editors using it also?

[bobzhang]

indeed, it should be placed in .vscode, can you confirm it works?

[mikaelbr]

This works as expected for me. Also fixed other deprecation warnings I got in vscode now.

[bobzhang]

thanks!