feat(docs) prepare api docs generation (backport #1741)

[mergify]

This is an automatic backport of pull request #1741 done by Mergify.
Cherry-pick of 9196f44 has failed:

On branch mergify/bp/release-1.1/pr-1741
Your branch is up to date with 'origin/release-1.1'.

You are currently cherry-picking commit 9196f4452.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   api/mesh/v1alpha1/circuit_breaker.proto
	modified:   api/mesh/v1alpha1/externalservice.proto
	modified:   api/mesh/v1alpha1/fault_injection.proto
	modified:   api/mesh/v1alpha1/health_check.proto
	modified:   api/mesh/v1alpha1/proxy_template.proto
	modified:   api/mesh/v1alpha1/retry.proto
	modified:   api/mesh/v1alpha1/timeout.proto
	modified:   api/mesh/v1alpha1/traffic_log.proto
	modified:   api/mesh/v1alpha1/traffic_permission.proto
	modified:   api/mesh/v1alpha1/traffic_route.proto
	modified:   api/mesh/v1alpha1/traffic_trace.proto

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   api/Makefile

To fix up this pull request, you can check it out locally. See documentation: https://help.github.com/articles/checking-out-pull-requests-locally/

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