Set isolatedModules in tsconfig.json

This silences the warnings of the form:
```
ts-jest[config] (WARN)
    The "ts-jest" config option "isolatedModules" is deprecated and will be removed in v30.0.0. Please use "isolatedModules: true" in /[...]/members-app/tsconfig.json instead, see https://www.typescriptlang.org/tsconfig/#isolatedModules
```

Author: chromy

jest.config.js

@@ -7,7 +7,6 @@ module.exports = {
       'ts-jest',
       {
         diagnostics: false,
-        isolatedModules: true,
       },
     ],
   },

tsconfig.json

@@ -18,7 +18,8 @@
     "forceConsistentCasingInFileNames": true,
     "composite": true,
     "allowUnusedLabels": false,
-    "allowUnreachableCode": false
+    "allowUnreachableCode": false,
+    "isolatedModules": true
   },
   "include": [
     "src/**/*.ts",