Note: this is under development
$ cd vscode
$ npm install
$ npx run tsc -p ./
$ cd ..
$ code --extensionDevelopmentPath=vscode/ .
Alternatively, you can do it in vscode itself.
$ cd vscode
$ code
And then press F5 to run another vscode with extension.
$ npm run package
$ npx vsce publish
See also: https://code.visualstudio.com/api/working-with-extensions/publishing-extension