docs: Include .md in internal links

Author: Michael Brewer

docs/index.md

@@ -141,18 +141,18 @@ aws serverlessrepo list-application-versions \
 
 | Utility | Description
 | ------------------------------------------------- | ---------------------------------------------------------------------------------
-| [Tracing](./core/tracer) | Decorators and utilities to trace Lambda function handlers, and both synchronous and asynchronous functions
-| [Logger](./core/logger) | Structured logging made easier, and decorator to enrich structured logging with key Lambda context details
-| [Metrics](./core/metrics) | Custom Metrics created asynchronously via CloudWatch Embedded Metric Format (EMF)
+| [Tracing](./core/tracer.md) | Decorators and utilities to trace Lambda function handlers, and both synchronous and asynchronous functions
+| [Logger](./core/logger.md) | Structured logging made easier, and decorator to enrich structured logging with key Lambda context details
+| [Metrics](./core/metrics.md) | Custom Metrics created asynchronously via CloudWatch Embedded Metric Format (EMF)
 | [Event handler](./core/event_handler) | Event handler decorators for common Lambda events
-| [Middleware factory](./utilities/middleware_factory) | Decorator factory to create your own middleware to run logic before, and after each Lambda invocation
-| [Parameters](./utilities/parameters) | Retrieve parameter values from AWS Systems Manager Parameter Store, AWS Secrets Manager, or Amazon DynamoDB, and cache them for a specific amount of time
-| [Batch processing](./utilities/batch) | Handle partial failures for AWS SQS batch processing
-| [Typing](./utilities/typing) | Static typing classes to speedup development in your IDE
-| [Validation](./utilities/validation) | JSON Schema validator for inbound events and responses
-| [Event source data classes](./utilities/data_classes) | Data classes describing the schema of common Lambda event triggers
-| [Parser](./utilities/parser) | Data parsing and deep validation using Pydantic
-| [Idempotency](./utilities/idempotency) | Idempotent Lambda handler
+| [Middleware factory](./utilities/middleware_factory.md) | Decorator factory to create your own middleware to run logic before, and after each Lambda invocation
+| [Parameters](./utilities/parameters.md) | Retrieve parameter values from AWS Systems Manager Parameter Store, AWS Secrets Manager, or Amazon DynamoDB, and cache them for a specific amount of time
+| [Batch processing](./utilities/batch.md) | Handle partial failures for AWS SQS batch processing
+| [Typing](./utilities/typing.md) | Static typing classes to speedup development in your IDE
+| [Validation](./utilities/validation.md) | JSON Schema validator for inbound events and responses
+| [Event source data classes](./utilities/data_classes.md) | Data classes describing the schema of common Lambda event triggers
+| [Parser](./utilities/parser.md) | Data parsing and deep validation using Pydantic
+| [Idempotency](./utilities/idempotency.md) | Idempotent Lambda handler
 
 ## Environment variables