2. add a dummy file tools.go to force "go mod vendor" to see
code-generator as dependencies
3. add a script to update CRD
4. add a README to document CRD updating steps
run go mod tidy
update README
A simple "go mod init && go mod tidy && go mod vendor" was enough and
mostly seems to have picked the same revisions of the dependencies as
before. Notable exceptions are klog and gogo/protobuf.
