Add index.md file with automation (#628)

This PR automates docsgen for this provider's installation doc.

Part of pulumi/home#3598.

Similar to pulumi/pulumi-newrelic#890, this is
probably blocked on
pulumi/pulumi-terraform-bridge#2466 due to
poor table rendering.

Update: This is awaiting the latest bridge; the table is rendered nicely
now:
<img width="750" alt="Screenshot 2024-11-11 at 10 49 14 AM"
src="https://github.com/user-attachments/assets/becb265c-0e7d-42ee-a89e-b1b49bd3127e">


- **first docsgen**
- **Remove TF-specific headers and clean up top-level Description**
- **Tweak regexp for header text matching**
- **Remove note as well**
- **Remove secrets warning**

.ci-mgmt.yaml

@@ -24,6 +24,7 @@ plugins:
   - name: std
     version: "1.6.2"
 pulumiConvert: 1
+registryDocs: true
 license:
   ignore:
     - github.com/databricks/terraform-provider-databricks/shim

Makefile

@@ -167,6 +167,10 @@ build_python: .make/build_python
 	@touch $@
 .PHONY: generate_python build_python
 
+# Run the bridge's registry-docs command to generated the content of the installation docs/ folder at provider repo root
+build_registry_docs:
+	$(WORKING_DIR)/bin/$(TFGEN) registry-docs --out $(WORKING_DIR)/docs
+
 clean:
 	rm -rf sdk/{dotnet,nodejs,go,python}
 	rm -rf bin/*