v2.19.0

New: Add support for PAC URL and windows registry (#712)

After some more usage of the proxy support I discovered a few issues,

1. Under windows, the information can be set in the registry instead of
using an environment variable.
2. Sometimes the information is provided as a PAC proxy. The URL points
basically to a configuration file that defines the location of the
proxy.
3. I tried setting PAC proxy directly and not messing around with
parsing it. Unfortunately, pupetter when downloading the browser does
not allow changing the proxy agent. This forced me to parse the
information from the PAC proxy.
4. Although I tested the previous PR under Linux working fine for
scraping, I had missed getting the information uploaded to YNAB. This PR
also updates the Network settings for unidici which is responsible for
pushing the information to YNAB.

I changed downloadChromium back to be proxy-agnostic. Setting the proxy
is now done at the backend level supporting both scraping and pushing.
I refactored the proxyConfig code to make it clearer in functionality
and set it as a directory under backend.