docs(changeset): add release notes

Author: gkoos

.changeset/chubby-snails-serve.md

@@ -0,0 +1,18 @@
+---
+'@gkoos/ffetch': major
+---
+
+Added
+
+- tracking of pending requests
+
+Changed
+
+- AbortSignal.any fallback fixed
+- timeout(0) properly handled (no timeout)
+- signal combining fixed
+
+Docs
+
+- documentation refactored and expanded
+- migration guide added