Functions page as a peer of Resources

[jkodroff]

We currently have the Functions page as sub-page of Resources. Since it's a "top-level" concept, it should be a peer of Resources.

• Create a top-level Functions overview page between "Resource Options" and "Inputs and Outputs" in the nav that explains the various types of functions you might use in a Pulumi program: provider functions, get functions, and resource methods.
• Move the existing provider functions content as a page beneath the new Functions overview page.
• Move the Get functions page beneath the new Functions overview page.
• Remove the JavaScript example from the Get functions page.
• Move the content for resource methods to a separate page. See if there's a way to say anything more about them to fill out the content (assuming there is something additional useful to say).

[thoward]

+1 to this