Please add VS Code variable substitution opt-in support for VS Code settings.json

[AG-Pupeza]

Please add opt-in support for VS-code settings variable substitution. For example in the vscode settings.json:

"autoDocstring.customTemplatePath": "${env:USERPROFILE}\Documents\template.mustache",

where ${env:USERPROFILE} gets replaced with the path to the user folder. Thanks in advance