update .gitignore for contrib directory
update .gitignore for contrib directory

hiunnhue/libchewing,PeterDaveHello/libchewing,hiunnhue/libchewing,bbyykk/libtaigi,cwlin/libchewing,dimotsai/libchewing,chewing/libchewing,mangokingTW/libchewing,chewing/libchewing,simonfork/libchewing,Chocobo1/libchewing,kito-cheng/libchewing,mangokingTW/libchewing,ShengYenPeng/libchewing,PeterDaveHello/libchewing,kito-cheng/libchewing,bbyykk/libtaigi,PingNote/libchewing,mangokingTW/libchewing,czchen/libchewing,ShengYenPeng/libchewing,hiunnhue/libchewing,cwlin/libchewing,simonfork/libchewing,cwlin/libchewing,yan12125/libchewing,ShengYenPeng/libchewing,simonfork/libchewing,ShengYenPeng/libchewing,chewing/libchewing,czchen/libchewing,robert501128/libchewing,robert501128/libchewing,bbyykk/libtaigi,kito-cheng/libchewing,Chocobo1/libchewing,cwlin/libchewing,robert501128/libchewing,czchen/libchewing,Chocobo1/libchewing,yan12125/libchewing,kito-cheng/libchewing,bbyykk/libtaigi,simonfork/libchewing,cwlin/libchewing,robert501128/libchewing,dimotsai/libchewing,PeterDaveHello/libchewing,Chocobo1/libchewing,PingNote/libchewing,PeterDaveHello/libchewing,PingNote/libchewing,chewing/libchewing,yan12125/libchewing,Chocobo1/libchewing,hiunnhue/libchewing,hiunnhue/libchewing,PingNote/libchewing,mangokingTW/libchewing,czchen/libchewing,yan12125/libchewing,bbyykk/libtaigi,dimotsai/libchewing,dimotsai/libchewing