add help to the Makefile

[jmrodri]

$ make help
Usage: make <OPTIONS> ... <TARGETS>

Available targets are:

build                Builds the starter pack
test                 Runs the tests
linux                Builds a Linux executable
image                Builds a Linux based image
clean                Cleans up build artifacts
push                 Pushes the image to dockerhub, REQUIRES SPECIAL PERMISSION
deploy-helm          Deploys image with helm
deploy-openshift     Deploys image to openshift
create-ns            Cleans up the namespaces
provision            Provisions a service instance
bind                 Creates a binding
help                 Shows the help

[jmrodri]

[jmrodri]

@pmorie I got bored before going home and decided to add the above.

[jmrodri]

@carolynvs glad it is helpful