add Buildpacks section for GIG #02
add Buildpacks section for GIG #02

Cloud Build supports pack command via community builder and requires additional preparation,
so only try on Cloud Shell
https://github.com/GoogleCloudPlatform/cloud-builders-community/tree/master/pack

google-cloud-japan/gig-training-materials,google-cloud-japan/gig-training-materials,google-cloud-japan/gig-training-materials,google-cloud-japan/gig-training-materials