more robust, pass "yarn valid-layers-check";

--- a/src/Tools/VSCode/extension/src/isabelle_encoding.ts	Tue Mar 08 17:09:09 2022 +0100
+++ b/src/Tools/VSCode/extension/src/isabelle_encoding.ts	Tue Mar 08 21:40:16 2022 +0100
@@ -7,6 +7,7 @@
 
 import { TextEncoder, TextDecoder } from 'util'   // VSCODE: REMOVE
 
+const process = require('process');
 const fs = require('fs');