[master] Format markdown (#24)
[master] Format markdown (#24)

Produced via:
  `prettier --write --prose-wrap=always $(find -name '*.md' | grep -v vendor | grep -v .github | grep -v docs/cmd/)`
/assign ZhiminXiang tcnghia
/cc ZhiminXiang tcnghia
knative-sandbox/net-certmanager,knative-sandbox/net-certmanager