docs: Add GitHub Releases page to project url metadata (#2099)

* Add https://github.com/scikit-hep/pyhf/releases to 'Project links' section
  on PyPI webpage.

Author: matthewfeickert

pyproject.toml

@@ -56,6 +56,7 @@ Documentation = "https://pyhf.readthedocs.io/"
 Homepage = "https://github.com/scikit-hep/pyhf"
 "Issue Tracker" = "https://github.com/scikit-hep/pyhf/issues"
 "Release Notes" = "https://pyhf.readthedocs.io/en/stable/release-notes.html"
+"Releases" = "https://github.com/scikit-hep/pyhf/releases"
 "Source Code" = "https://github.com/scikit-hep/pyhf"
 
 [project.optional-dependencies]