Docs file and folder names should consistently be in kebabe-case rather than snake_case

[chalin]

Most file/folders use hyphens as separator:

$ find docs -name "*-*"
docs/cloud-providers
docs/cloud-providers/aws-sdk.md
docs/database/database-metrics.md
docs/database/database-spans.md
docs/cloudevents/cloudevents-spans.md
docs/general/general-attributes.md
docs/general/metrics-general.md
docs/general/trace-compatibility.md
docs/general/trace-general.md
docs/general/logs-general.md
docs/general/events-general.md
docs/feature-flags
docs/feature-flags/feature-flags-spans.md
docs/feature-flags/feature-flags-logs.md
docs/faas/faas-metrics.md
docs/faas/aws-lambda.md
docs/faas/faas-spans.md
docs/object-stores
docs/exceptions/exceptions-spans.md
docs/exceptions/exceptions-logs.md
docs/system/hardware-metrics.md
docs/system/system-metrics.md
docs/system/runtime-environment-metrics.md
docs/system/process-metrics.md
docs/http/http-metrics.md
docs/http/http-spans.md
docs/rpc/rpc-spans.md
docs/rpc/connect-rpc.md
docs/rpc/json-rpc.md
docs/rpc/rpc-metrics.md
docs/messaging/messaging-spans.md

The following, which should be renamed, use an underscore as a separator:

$ find docs -name "*_*"               
docs/resource/deployment_environment.md
docs/resource/cloud_provider
docs/resource/cloud_provider/gcp/cloud_run.md

/cc @svrnm @cartermp

[Oberon00]

If we do this, we should also add a "lint" (could be just a shell script based check) for it

[chalin]

@Oberon00 - I've added a check target to the Makefile in #177, and added the check to the markdownlint GH action.