HOTFIX FOR ELECTRON CVEs

This is a hotfix that updates a vulnerable Electron version to a safe one. This
is in response to a row of CVEs that have been detected in the source code of
Chromium in the past days. With an outdated Electron-version (<12.0.6), it was
possible for an attacker to take over your computer via Zettlr using a crafted
HTML webpage.

This release fixes Zettlr 1.8.7, which was vulnerable to this kind of attack. It
upgrades Electron from a vulnerable 11.x.x-version to the safe version 12.0.6.

DO NO LONGER USE ZETTLR 1.8.7! RELEASES PRIOR TO 1.8.8 MUST BE REGARDED AS UNSAFE!