BlueOcean 1.19

• JENKINS-58085 - Fix issue where stages are shown as waiting to start when they are running/completed (#2017) @dwnusbaum
• validate 'run.causes' is set before checking length (#2020) @kevinushey
• JENKINS-58684 - use sse gateway 1.20 (#2021) @olamy
• Prepare for next release (#2012) @halkeye
• JENKINS-55605 - Remove restriction that prevented clicking/url updating on unfinished nodes, or parallel nodes (#2018) @halkeye
• Update README.md w/ note about installation on macOS (#2016) @heisian
• address error.responseBody is undefined (#2015) @heisian

🐛 Bug Fixes

• JENKINS-53352 - fix test whitespace rendering on junit files (#1988) @egonelbre