[editorial] Add headings to configauth/README.md (#12309)

- Adds headings so as to have anchor IDs that the docs can refer to.
- This is proposed, in part, to help address
open-telemetry/opentelemetry.io#6234

/cc @open-telemetry/docs-maintainers

config/configauth/README.md

@@ -5,21 +5,24 @@ This module defines necessary interfaces to implement server and client type aut
 - Server type authenticators perform authentication for incoming HTTP/gRPC requests and are typically used in receivers.
 - Client type authenticators perform client-side authentication for outgoing HTTP/gRPC requests and are typically used in exporters.
 
-The currently known authenticators are:
+The currently known authenticators are listed below.
 
-- Server Authenticators
-  - [Basic Auth Extension](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/extension/basicauthextension)
-  - [Bearer Token Extension](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/extension/bearertokenauthextension)
-  - [OIDC Extension](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/extension/oidcauthextension)
+## Server Authenticators
 
-- Client Authenticators
-  - [ASAP Client Authentication Extension](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/extension/asapauthextension)
-  - [Basic Auth Extension](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/extension/basicauthextension)
-  - [Bearer Token Extension](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/extension/bearertokenauthextension)
-  - [OAuth2 Client Extension](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/extension/oauth2clientauthextension)
-  - [Sigv4 Extension](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/extension/sigv4authextension)
+- [Basic Auth Extension](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/extension/basicauthextension)
+- [Bearer Token Extension](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/extension/bearertokenauthextension)
+- [OIDC Extension](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/extension/oidcauthextension)
+
+## Client Authenticators
+
+- [ASAP Client Authentication Extension](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/extension/asapauthextension)
+- [Basic Auth Extension](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/extension/basicauthextension)
+- [Bearer Token Extension](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/extension/bearertokenauthextension)
+- [OAuth2 Client Extension](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/extension/oauth2clientauthextension)
+- [Sigv4 Extension](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/extension/sigv4authextension)
+
+Example:
 
-Examples:
 ```yaml
 extensions:
   oidc: