[Feature Request] Allow relative file paths in preference.json

[redsigma]

It would be nice if i can use paths such as below

{
  "Locale": "en_US",
  "Theme": "Default",
  "ThemeOverrides": ".\\themedark.json",
  "GitInstallPath": ".\\git\\bin\\git.exe",
  "ShellOrTerminalPath": ".\\git\\bin\\git-bash.exe"
}

Optionally It would be even better if it can also allow for environment variables

{
  "Locale": "en_US",
  "Theme": "Default",
  "ThemeOverrides": ".\\themedark.json",
  "GitInstallPath": "$GIT_PATH\\git.exe",
  "ShellOrTerminalPath": "$GIT_PATH\\git-bash.exe"
}