Update pac-resolver to v5.0.0

Fixes CVE-2021-23406: GHSA-9j49-mfvp-vmhm

Modernise proxy code

Merge pull request alexjurkiewicz#8 from pzi/feature/add-ignore-list

Feature: Ignore list

Merge pull request alexjurkiewicz#5 from pzi/feature/document-IAM-per…

…missions

Add required permissions section to README

Merge pull request alexjurkiewicz#2 from pzi/master

Don't use undefined as variable name

Bump version to v1.2.0

You could argue changing the default threshold from medium -> high is a
breaking change. I'll probably treat it as such in the future when this
action has users other than me...

Add output for non-failing jobs

Tweak descriptions