editors/vscode: enable signature verification of extensions installed from Open VSX Registory

Code - OSS tries to use the Microsoft's proprietary node module
"@vscode/vsce-sign" for verifying a signature when a user tries to
install an extension. The node module is not available on FreeBSD so
the verification fails and a dialog notifying that "Cannot install
extesion" appears.

By using "node-ovsx-sign" module instead of the proprietary one, Code

• OSS can properly verify the signature and the installation of an

extension succeeds.

PR: 289337
Reported by: mandree
Obtained from: https://github.com/termux/termux-packages/pull/24757