add Dockerfile instructionss to build slang
add Dockerfile instructionss to build slang

natabeck/cloud-slang,shajyhia/score-language,narry/cloud-slang,CloudSlang/cloud-slang,narry/cloud-slang,natabeck/cloud-slang,CloudSlang/cloud-slang,jrosadohp/cloud-slang,CloudSlang/cloud-slang,CloudSlang/cloud-slang,shajyhia/score-language,jrosadohp/cloud-slang