fix: Enable control of docs by provider authors

This enables the Docker provider to explicitly embed `{{% examples %}}` after
introductory text, unblocking:
- pulumi/pulumi-docker#592
- pulumi/pulumi-docker#588

This fix addresses this issue:
- pulumi/pulumi-docker#600

All of these might be fixed by a change to Docker that added introductory text
above examples, but as observed in pulumi/pulumi-docker#600, it's not currently
possible to render text outside of an examples block.

This change to docs rendering allows us to explicitly add the examples shortcode
block in the input docs, and pass-through tfgen rendering entirely.

pkg/tfgen/docs.go

@@ -1085,6 +1085,12 @@ func (g *Generator) convertExamples(docs, name string, stripSubsectionsWithError
 		return ""
 	}
 
+	if strings.Contains(docs, "{{% examples %}}") {
+		// The provider author has explicitly written an entire markdown document including examples.
+		// We'll just return it as is.
+		return docs
+	}
+
 	if strings.Contains(docs, "```typescript") || strings.Contains(docs, "```python") ||
 		strings.Contains(docs, "```go") || strings.Contains(docs, "```yaml") ||
 		strings.Contains(docs, "```csharp") || strings.Contains(docs, "```java") {