Improve type definitions for the viewer

[ex37]

This commit improves compatibility of the viewer code with TypeScript by including missing type imports/definitions and correcting existing ones

[Snuffleupagus]

Given that the default viewer is not intended to be directly used by third-parties, and thus isn't included in pdfjs-dist, I don't know if this is really desirable. Please see http://mozilla.github.io/pdf.js/getting_started/#introduction (emphasis mine):

The viewer is built on the display layer and is the UI for PDF viewer in Firefox and the other browser extensions within the project. It can be a good starting point for building your own viewer. However, we do ask if you plan to embed the viewer in your own site, that it not just be an unmodified version. Please re-skin it or build upon it.

[ex37]

@Snuffleupagus this could help people who want to extend the viewer. Plus there are also lots of nice utils within the web folder. Also added jsdoc types could be helpful for project's contributors.

But if you think this is not within the scope of the project, we can remove the entrypoint, and just add the type fixes.

[Snuffleupagus]

But if you think this is not within the scope of the project, we can remove the entrypoint, and just add the type fixes.

That'd be a requirement as far as I'm concerned. Please note that the existing type definitions are unused within the PDF.js project, but has nonetheless added a bunch of work for the core contributors; hence we don't want to further increase that.

Also, please make sure to write a good commit message.

[ex37]

Addressed requested changes, changed commit message / pr name.
Also added eslint-disable-next-line where needed.

[Snuffleupagus]

https://github.com/mozilla/pdf.js/wiki/Squashing-Commits

[ex37]

squashed

[timvandermeij]

Before we can merge this please also include a better commit message. The guidelines at https://cbea.ms/git-commit/ could help with this. The commit message should primarily contain which change is being made and why; implementation details like which files or classes are changed can usually be left out because that's already clear from the commit diff.

The following commit message (or something similar) could be a suggestion here:

Improve type definitions for the viewer

This commit improves compatibility of the viewer code with TypeScript by
including missing type imports/definitions and correcting existing ones.

[ex37]

Got it. Set to your suggested description, as it fully describes what this pr is about.

[timvandermeij]

Looks good to me with the comments below addressed, but given the original review I'll leave the final approval to @Snuffleupagus. Thanks!

[ex37]

removed the default value for hidden, and also added missing extensions

[ex37]

@timvandermeij in my opinion a proper fix for _addToggleButton method would probably be separating it into two methods, which will be using same signature across inheriting classes. Other than type definitions, in my understanding, it can also help with runtime optimizations. But yes, that's outside of this pr scope.

[Snuffleupagus]

r=me, thanks.