added a note on how to use gulp for js editing
added a note on how to use gulp for js editing

kzantow/blueocean-plugin,jenkinsci/blueocean-plugin,tfennelly/blueocean-plugin,tfennelly/blueocean-plugin,kzantow/blueocean-plugin,jenkinsci/blueocean-plugin,alvarolobato/blueocean-plugin,jenkinsci/blueocean-plugin,ModuloM/blueocean-plugin,kzantow/blueocean-plugin,ModuloM/blueocean-plugin,tfennelly/blueocean-plugin,alvarolobato/blueocean-plugin,alvarolobato/blueocean-plugin,jenkinsci/blueocean-plugin,jenkinsci/blueocean-plugin,alvarolobato/blueocean-plugin,kzantow/blueocean-plugin,ModuloM/blueocean-plugin,ModuloM/blueocean-plugin,tfennelly/blueocean-plugin