add experimental-strip-types in app-ts-esm

[SimoneDevkt]

I modified the app-ts-esm template by inserting the indicated tsconfig
https://nodejs.org/en/learn/typescript/run-natively#running-typescript-code-with-nodejs and erasableSyntaxOnly.
This way the dev script can directly launch the ts file with --experimental-strip-types

Checklist

• run npm run test and npm run benchmark
• tests and/or benchmarks are included
• documentation is changed or added
• commit message and code follows the Developer's Certification of Origin
  and the Code of conduct

[ilteoood]

I don't think that we should introduce the --experimental-strip-types.
That flag is available from node 22.6, but fastify still support also node 20.

[kibertoad]

it is coming to node 20 soon

[mcollina]

Once strip types ships in Node v20, I'd recommend shipping a new version of this as a semver-major.

[mcollina]

Why is FASTIFY_AUTOLOAD_TYPESCRIPT=1 needed?

[SimoneDevkt]

Why is FASTIFY_AUTOLOAD_TYPESCRIPT=1 needed?

I tried to run it without this flag, but I got an error. I don't know why

Error: @fastify/autoload cannot import plugin at '***\fastify-cli\test1\src\plugins\sensible.ts'. To fix this error compile TypeScript to JavaScript or use 'ts-node' to run your app.
    at handleTypeScriptSupport (***\fastify-cli\node_modules\@fastify\autoload\lib\find-plugins.js:152:11)
    at processFile (***\fastify-cli\node_modules\@fastify\autoload\lib\find-plugins.js:124:3)
    at processDirContents (***\fastify-cli\node_modules\@fastify\autoload\lib\find-plugins.js:101:7)
    at buildTree (***\fastify-cli\node_modules\@fastify\autoload\lib\find-plugins.js:41:9)
    at async findPlugins (***\fastify-cli\node_modules\@fastify\autoload\lib\find-plugins.js:14:3)
    at async autoload (***\fastify-cli\node_modules\@fastify\autoload\index.js:20:22)

https://github.com/fastify/fastify-autoload?tab=readme-ov-file#override-typescript-detection-using-an-environment-variable

[mcollina]

fastify/fastify-autoload#442 < I think fastify-autoload would need some fixing. I think we can access process.features to detect if there is the support instead of relying on the version number.