docs(META): update PR template to mention an existing issue
docs(META): update PR template to mention an existing issue

cyclejs/cyclejs,cyclejs/cycle-core,staltz/cycle,cyclejs/cyclejs,cyclejs/cycle-core,ntilwalli/cyclejs,cyclejs/cyclejs,ntilwalli/cyclejs,ntilwalli/cyclejs,cyclejs/cyclejs,ntilwalli/cyclejs,staltz/cycle