To make it easier to tell which PDF.js version/commit that the *built* files correspond to, they have (since many years) included `pdfjsVersion` and `pdfjsBuild` constants with that information.
As currently implemented this has a few shortcomings:
- It requires manually adding the code, with its preprocessor statements, in all relevant files.
- It requires ESLint disable statements, since it's obviously unused code.
- Being unused, this code is removed in the minified builds.
- This information would be more appropriate as comments, however Babel discards all comments during building.
- It would be helpful to have this information at the top of the *built* files, however it's being moved during building.
To address all of these issues, we'll instead utilize Webpack to insert the version/commit information as a comment placed just after the license header.
To avoid problems with `export` statements in the QuickJS Javascript Engine, we can work-around that by *explicitly* exposing `pdfjsScripting` globally instead.
This brings the new `pdf.scripting.js` bundling more in-line with the pre-existing handling for the `pdf.js`/`pdf.worker.js` files:
- Add a new `src/pdf.scripting.js` file as the entry-point for the build scripts.
- Add the version/build numbers at the top of the *built* `pdf.scripting.js` files, since all other built files include that information given that it's often helpful to be able to easily determine the *exact* version.
- Tweak the `createScriptingBundle` in the gulp-file, since it looks like a little bit too much copy-and-paste in the variable names.
