Adding "Data Source" header to data source resources.

[RavenAlly]

Related issue: hashicorp/terraform-website#18

[bflad]

👍 personally. Thank you! Totally not necessary in this PR but it'd be nice to clean up the extraneous slashes in the titles too

[Ninir]

Hi @RavenAlly

I do think this is a good idea to better identify whether you're on a resource or a data source 👍

Since it needs to be reflected among other providers, just would like to call @sethvargo here and know what he thinks of it if you don't mind: perhaps he even has an approach to deal with this :).
Seth manages many things at HashiCorp, but worked a lot on the website, so just wondering!

[catsby]

Thank you! I'm closing this in favor of #2713 that I just opened, it's this PR but with a commit where I merge master and resolve the above merge conflicts.

[ghost]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.

If you feel this issue should be reopened, we encourage creating a new issue linking back to this one for added context. Thanks!