Copy Jenkinsfile.xml to your filetypes folder, and restart PyCharm
~/Library/Preferences/PyCharmXX/filetypes
~/.PyCharmXX/config/filetypes
%HOMEPATH%\\.PyCharmXX\config\filetypes
~/Library/Application Support/JetBrains/PyCharmXX/filetypes
~/.config/JetBrains/PyCharmXX/filetypes
%APPDATA%\JetBrains\PyCharmXX\filetypes