Add changelog entry for wpsharks/comet-cache#879

CHANGELOG.md

@@ -1,6 +1,7 @@
 = $v =
 
 - **Bug Fix**: The Statistics feature was broken when the PHP `disk_total_space()` and/or `disk_free_space()` functions were disabled by the PHP configuration. Comet Cache now handles this scenario gracefully by hiding disk-related stats when those functions are not allowed. See [Issue #775](https://github.com/websharks/comet-cache/issues/775)
+- **Compatibility:** Many improvements to the Pro software update system, including changes to the API Endpoints and the Proxy Fallback endpoint. See [Issue #879](https://github.com/websharks/comet-cache/issues/879) and [Issue #315](https://github.com/websharks/comet-cache-pro/pull/315) for full details.
 
 = v170220 =