Function resolvePlatformRoot

resolvePlatformRoot(currentDir: string, fallbackPath: string): string
Resolve platform root directory (the monorepo root) by searching upward for a package.json with workspaces.

ANGULAR_MODERNIZER_PLATFORM_ROOT takes precedence when set; without a match the fallback path relative to currentDir is used.
Parameters
- currentDir: string
  Starting directory for upward search (typically __dirname)
- fallbackPath: string
  Fallback relative path if monorepo root not found (e.g., '../../../..')
Returns string
Absolute path to platform root directory
Example
```
import { fileURLToPath } from 'node:url';
import * as path from 'node:path';

const __filename = fileURLToPath(import.meta.url);
const __dirname = path.dirname(__filename);

const platformRoot = resolvePlatformRoot(__dirname, '../../../..');
```