update plugin configspec docs

website/source/docs/extending/custom-builders.html.md

@@ -36,6 +36,12 @@ type Builder interface {
   Run(context.Context, ui Ui, hook Hook) (Artifact, error)
 }
 ```
+### The "ConfigSpec" Method
+
+This method returns a hcldec.ObjectSpec, which is a spec necessary for using
+HCL2 templates with Packer. For information on how to use and implement this
+function, check our
+[object spec docs](https://www.packer.io/guides/hcl/component-object-spec)
 
 ### The "Prepare" Method
 

website/source/docs/extending/custom-post-processors.html.md

@@ -42,6 +42,13 @@ type PostProcessor interface {
 }
 ```
 
+### The "ConfigSpec" Method
+
+This method returns a hcldec.ObjectSpec, which is a spec necessary for using
+HCL2 templates with Packer. For information on how to use and implement this
+function, check our
+[object spec docs](https://www.packer.io/guides/hcl/component-object-spec)
+
 ### The "Configure" Method
 
 The `Configure` method for each post-processor is called early in the build
@@ -92,6 +99,6 @@ return value is explained below:
     keep the artifact around.
 -   `bool` - If forceOverride is true, then any user input for
     keep_input_artifact is ignored and the artifact is either kept or discarded
-    according to the value set in `keep`. 
+    according to the value set in `keep`.
 -   `error` - Non-nil if there was an error in any way. If this is the case,
     the other two return values are ignored.

website/source/docs/extending/custom-provisioners.html.md

@@ -67,6 +67,13 @@ validate the configuration.
 The `Prepare` method is called very early in the build process so that errors
 may be displayed to the user before anything actually happens.
 
+### The "ConfigSpec" Method
+
+This method returns a hcldec.ObjectSpec, which is a spec necessary for using
+HCL2 templates with Packer. For information on how to use and implement this
+function, check our
+[object spec docs](https://www.packer.io/guides/hcl/component-object-spec)
+
 ### The "Provision" Method
 
 The `Provision` method is called when a machine is running and ready to be
@@ -79,6 +86,10 @@ connected at this point.
 
 The provision method should not return until provisioning is complete.
 
+The map[string]interface{} provides users with build-specific information,
+like host and IP, provided by the `build` template engine. Provisioners may use
+this information however they please, or not use it.
+
 ## Using the Communicator
 
 The `packer.Communicator` parameter and interface is used to communicate with