fix(@schematics/angular): enable TypeScript skipLibCheck in new workspace

This commit enables `skipLibCheck` in new workspaces which is now recommanded by TypeScript.  When enabled, type checking of declaration files is skipped as rather than doing a full check of all `d.ts` files, TypeScript will type check the code you specifically refer to in your app’s source code.

See: https://www.typescriptlang.org/tsconfig#skipLibCheck

Author: alan-agius4

packages/schematics/angular/workspace/files/tsconfig.json.template

@@ -9,6 +9,7 @@
     "noPropertyAccessFromIndexSignature": true,
     "noImplicitReturns": true,
     "noFallthroughCasesInSwitch": true,<% } %>
+    "skipLibCheck": true,
     "esModuleInterop": true,
     "sourceMap": true,
     "declaration": false,