Try to fix TypeScript definitions for the es5-build in pdfjs-dist (issue 12872)

[Snuffleupagus]

Given that we're already using the external/dist/ folder for things we simply want to copy to pdfjs-dist during building, this patch should hopefully work since it's based on the suggestion in #12827 (comment).

As long as this only requires a single/small file, to fix the TypeScript definitions in es5-builds, this solution seem acceptable as far as I'm concerned. (Although, please note that I don't know enough about TypeScript to actually test the patch.)

Fixes #12827

[timvandermeij]

Let's do this; thanks!

[simonhaenisch]

Somehow this file is not part of pdfjs-dist, or at least not anymore:

❯ ls node_modules/pdfjs-dist/es5/build
pdf.js
pdf.js.map
pdf.min.js
pdf.worker.entry.js
pdf.worker.js
pdf.worker.js.map
pdf.worker.min.js

(see https://github.com/mozilla/pdfjs-dist/tree/7bfceb110b9b27a09cc3d69f4907c59fd5561f0c/es5/build)

I couldn't figure out where the build script for pdfjs-dist lives but is it possible that it's just forgetting to include this file/file extension in the output?

---

FWIW, re the original issue #12827: there's also the official browser field in package.json (see https://docs.npmjs.com/cli/v7/configuring-npm/package-json#browser), so it could be

{
  "main": "es5/build/pdf.js",
  "browser": "build/pdf.js",
  "types": "types/pdf.d.ts",
  "//": "..."
}

However I'm not totally sure about the implications of this, i. e. how well browser is supported by other tools (should be pretty good support though).

[simonhaenisch]

Hm actually never mind I just figured out that the latest stable release (2.6.347) was from 5 months ago... the file is there now that I installed pdfjs-dist@next (2.7.570).