mention field addition in breaking API changes

Author: simonbyrne

CHANGELOG.md

@@ -150,7 +150,8 @@ v0.25
   If this is `NULL`, then it will not be called and the `exists` function
   will be used instead.
 
-* `git_remote_connect()` now accepts proxy options.
+* `git_remote_connect()` now accepts `git_proxy_options` argument, and
+  `git_fetch_options` and `git_push_options` each have a `proxy_opts` field.
 
 v0.24
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