[PatternFly] The PatternFly v3.23.0 Release is now available

[Daniel Labrecque]

The UXD team is proud to announce the 3.23.0 release of PatternFly. This release includes the following changes.

# Release Notes

## Enhancements
- Update the icon files and CSS icon definitions #612
- Add masthead utility links on the vertical nav on small viewports #615: This PR is related to this jira issue and fixes #496

## Bug Fixes
- Remove the "open new window" icon in the header of the vertical nav test pages #611
- Links on the vertical nav mast head are blue #610: they should be light grey.
- Kebab menu in Toast Notifications is not vertically aligned with the text #609
- autoprefixer: support old firefox versions and placeholder fix #614: This fix adds other Firefox version prefixes to autoprefixer that were missed before, along with a fix for form-control::placeholder prefixed css

Check out the PatternFly 3.23.0 Release Notes for more details:
https://github.com/patternfly/patternfly/releases/tag/v3.23.0

Thanks to everyone who participated in this release (both directly and indirectly) - your contributions are what keeps pushing PatternFly forward!

- The Red Hat UXD team