Add newman, k6 and, postman-to-k6 command to image flagger-loadtester

Dockerfile

FROM weaveworks/flagger-loadtester:0.12.0
USER root
RUN apk update && apk add nodejs npm gettext
RUN npm install -g newman
RUN npm install postman-to-k6
COPY --from=loadimpact/k6:latest /usr/bin/k6 /usr/bin/k6
COPY scripts .
USER app

hey .. did you incorporate flagger with your postman colelction