add changelog for v3 agent-endpoints

docs/agent/changelog.md

@@ -6,6 +6,18 @@ title: Changelog
 
 ## v3
 
+### ngrok Agent 3.15.0 - \[2024-08-29\]
+
+- Added `--url` agent CLI flag for simpler creation of HTTP(S), TLS, and TCP protocol endpoints.
+- Deprecated `--domain`, `--scheme`, and `--remote-addr` agent CLI flags, which have been replaced by `--url`.
+- Added `--metadata` and `--description` agent CLI flags when using `--url`.
+##### A new agent configuration format added to V3
+  - Added `agent:` as a toplevel field to agent config, with `endpoints:` as a nested field for easier [endpoint creation](/docs/agent/config/#full-example).
+  - v3 supports _both_ tunnels and endpoints. Tunnels are now considered deprecated when using config v3.
+  - Some global configuration fields renamed in v3 when used under the `agent:` field.
+  - v2 still supported, but does not support the new `endpoints:` field.
+- Added support for [endpoint fields](/docs/api/resources/endpoints/#list-endpoints) in ngrok's `api`.
+
 ### ngrok Agent 3.14.0 - \[2024-08-01\]
 
 - Added support for `traffic_policy` field in agent config for Traffic Policy configuration.