Document unsupported resources

[plumdog]

The supported resources are documented here https://github.com/DataDog/datadog-sync-cli#supported-resources, but I would like to see a list of resources that a user might expect to be handled by this tool but aren't. I found that #189 lists some of these resources.

For example, log views are not migrated, but I think they would be a valid resource for this tool to migrate. However, there are things like logs and metrics are out of scope for this tool.

Ideally, this would be a table of all of the resources within Datadog, with a note for each of supported/not yet supported (link to GitHub issue)/out of scope.

Eg:

resource	status
...	...
logs_indexes	supported
logs_views	not yet supported #xyz
logs	out of scope
...	...
metrics	out of scope
metric_tag_configurations	supported
metric_metadatas	not yet support #xyz
...	...