Migrate from PhantomJS

[aumouvantsillage]

PhantomJS is deprecated and it seems to cause issues for some users.
We need to migrate Sozi-export to another headless browser.

We have the following options:

• SlimerJS could be used with little effort, but it requires users to install Firefox and is not compatible with recent versions of Firefox.
• Headless Chromium, through the puppeteer module, which may require more effort but should be more stable.
• Nightmare

[aumouvantsillage]

Additional, and preferred option:

• Migrate the export feature to the Sozi editor, using the methods printToPDF and capturePage provided by Electron.