Suggest the correct markdownlint CLI (#1520)
Suggest the correct markdownlint CLI (#1520)

* Suggest the correct markdownlint CLI

So the developers can run `make markdownlint` to lint the files.

* Fix instructions

Co-authored-by: Bogdan Drutu <3f8e17047c2434e5c82a61403e56b9ef3e226d99@gmail.com>
open-telemetry/opentelemetry-specification,open-telemetry/opentelemetry-specification