New endpoint to get info on latest Zotero version

[Dan Stillman]

We've added a new endpoint that allows third-party packagers and other
tools to check the latest available Zotero version:

https://www.zotero.org/download/client/version?channel=release

Or for a specific architecture:

https://www.zotero.org/download/client/version?channel=release&platform=linux-arm64

Same pattern for the 'beta' channel

Previously, there was a JSON file used by some packagers (e.g.,
zotero-deb), but it didn't reliably reflect the version being made
available to users via the official download page. The above URLs will.

We do have separate logic that determines whether a given Zotero version
gets served as an auto-update (e.g., Zotero 9 is not yet pushed as an
auto-update, despite being current version on the download page and
available via Help → "Check for Updates…" within Zotero), but as far as
I know no external package managers would be able to make a distinction
between the current version and the version that should be offered to
existing users. If that is possible, let us know and we can discuss ways
to expose that logic.