backport(docs): add description to provider index page (#280)

* Update docs to clarify Coder templates and workspaces

- Add description to index files.
- Link to Coder templates and workspaces documentation.

* Update docs/index.md

* Apply suggestions from code review

Author: matifali

Diff for: docs/index.md

@@ -3,11 +3,13 @@
 page_title: "Coder Provider"
 subcategory: "Infrastructure"
 description: |-
-  
+    Terraform provider for defining Coder templates, which are the underlying infrastructure for Coder workspaces.
 ---
 
 # Coder Provider
 
+Terraform provider for defining Coder [templates](https://coder.com/docs/templates), which are the underlying infrastructure for Coder [workspaces](https://coder.com/docs/workspaces).
+
 ## Example
 
 ```terraform

Diff for: templates/index.md.tmpl

@@ -3,11 +3,13 @@
 page_title: "Coder Provider"
 subcategory: "Infrastructure"
 description: |-
-  
+    Terraform provider for defining Coder templates, which are the underlying infrastructure for Coder workspaces.
 ---
 
 # Coder Provider
 
+Terraform provider for defining Coder [templates](https://coder.com/docs/templates), which are the underlying infrastructure for Coder [workspaces](https://coder.com/docs/workspaces).
+
 ## Example
 
 {{tffile "examples/provider/provider.tf"}}