fix: ensure TsconfigPathsPlugin is only added if tsconfig.json exists

[adamstankiewicz]

The release of 14.4.0 to make Webpack and ESlint aware of paths defined in tsconfig.json breaks MFEs that have not yet adopted TypeScript, as described here. If a project does't define tsconfig.json, tsconfig-paths-webpack-plugin will unexpectedly throw an error due to the missing file.

> @edx/frontend-app-learner-dashboard@0.0.1 build
> fedx-scripts webpack

Running with resolved config:
/home/runner/work/frontend-app-learner-dashboard/frontend-app-learner-dashboard/webpack.prod.config.js

[webpack-cli] Failed to load '/home/runner/work/frontend-app-learner-dashboard/frontend-app-learner-dashboard/webpack.prod.config.js' config
[webpack-cli] Error: ENOENT: no such file or directory, stat 'tsconfig.json'
    at Object.statSync (node:fs:1[6](https://github.com/openedx/frontend-app-learner-dashboard/actions/runs/14122223957/job/39564410662?pr=569#step:8:7)67:25)
    at resolveConfigPath (/home/runner/work/frontend-app-learner-dashboard/frontend-app-learner-dashboard/node_modules/tsconfig-paths-webpack-plugin/node_modules/tsconfig-paths/lib/tsconfig-loader.js:56:12)
    at loadSyncDefault (/home/runner/work/frontend-app-learner-dashboard/frontend-app-learner-dashboard/node_modules/tsconfig-paths-webpack-plugin/node_modules/tsconfig-paths/lib/tsconfig-loader.js:33:22)
    at tsConfigLoader (/home/runner/work/frontend-app-learner-dashboard/frontend-app-learner-dashboard/node_modules/tsconfig-paths-webpack-plugin/node_modules/tsconfig-paths/lib/tsconfig-loader.js:2[7](https://github.com/openedx/frontend-app-learner-dashboard/actions/runs/14122223957/job/39564410662?pr=569#step:8:8):22)
    at configLoader (/home/runner/work/frontend-app-learner-dashboard/frontend-app-learner-dashboard/node_modules/tsconfig-paths-webpack-plugin/node_modules/tsconfig-paths/lib/config-loader.js:2[8](https://github.com/openedx/frontend-app-learner-dashboard/actions/runs/14122223957/job/39564410662?pr=569#step:8:9):22)
    at Object.loadConfig (/home/runner/work/frontend-app-learner-dashboard/frontend-app-learner-dashboard/node_modules/tsconfig-paths-webpack-plugin/node_modules/tsconfig-paths/lib/config-loader.js:8:12)
    at loadConfig (/home/runner/work/frontend-app-learner-dashboard/frontend-app-learner-dashboard/node_modules/tsconfig-paths-webpack-plugin/lib/plugin.js:86:36)
    at new TsconfigPathsPlugin (/home/runner/work/frontend-app-learner-dashboard/frontend-app-learner-dashboard/node_modules/tsconfig-paths-webpack-plugin/lib/plugin.js:35:26)
    at Object.<anonymous> (/home/runner/work/frontend-app-learner-dashboard/frontend-app-learner-dashboard/node_modules/@openedx/frontend-build/config/webpack.common.config.js:50:7)
    at Module._compile (node:internal/modules/cjs/loader:152[9](https://github.com/openedx/frontend-app-learner-dashboard/actions/runs/14122223957/job/39564410662?pr=569#step:8:10):14) {
  errno: -2,
  code: 'ENOENT',
  syscall: 'stat',
  path: 'tsconfig.json'
}

This PR ensures tsconfig-paths-webpack-plugin is only included in webpack.common.config.js if a root tsconfig.json file exists for a project.

Testing Instructions

1. Run npm run build for the example MFE app included with this project with the included ./example/tsconfig.json file.
2. Observe it builds successfully.
3. Temporarily delete the ./example/tsconfig.json file, and change the @src/App import to ./App.
4. Re-run npm run build for the example MFE.
5. Observe it will now build successfully; previously, it would not.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 0.00%. Comparing base (cd49b15) to head (8457337).
Report is 1 commits behind head on master.

Additional details and impacted files

@@      Coverage Diff      @@
##   master   #643   +/-   ##
=============================
=============================

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[openedx-semantic-release-bot]

🎉 This PR is included in version 14.4.1 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀

[openedx-semantic-release-bot]

🎉 This PR is included in version 15.0.0-alpha.27 🎉

The release is available on:

• npm package (@alpha dist-tag)
• GitHub release

Your semantic-release bot 📦🚀