Fix headers in README.md

Author: JosephTLyons

README.md

@@ -11,11 +11,11 @@ The protocol is still under heavy development, and we aim to mature it as we get
 
 ACP is a protocol intended for broad adoption across the ecosystem; we follow a structured process to ensure changes are well-considered.
 
-## Pull Requests
+### Pull Requests
 
 Pull requests should intend to close an existing [issue](https://github.com/zed-industries/agent-client-protocol/issues).
 
-## Issues
+### Issues
 
 - **Bug Reports**: If you notice a bug in the protocol, please file an [issue](https://github.com/zed-industries/agent-client-protocol/issues/new?template=05_bug_report.yml) and we will be in touch.
 - **Protocol Suggestions**: If you'd like to propose additions or changes to the protocol, please start a [discussion](https://github.com/zed-industries/agent-client-protocol/discussions/categories/protocol-suggestions) first. We want to make sure proposed suggestions align well with the project. If accepted, we can have a conversation around the implementation of these changes. Once that is complete, we will create an issue for pull requests to target.