Add note about current development state (#652)

* docs: Add note about current state

* fix: Improve wording

Co-authored-by: Jesse Braham <jessebraham@users.noreply.github.com>

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Co-authored-by: Jesse Braham <jessebraham@users.noreply.github.com>

README.md

@@ -8,6 +8,10 @@ Serial flasher utilities for Espressif devices, based loosely on [esptool.py](ht
 
 Supports the **ESP32**, **ESP32-C2/C3/C6**, **ESP32-H2**, **ESP32-P4**, and **ESP32-S2/S3**.
 
+> [!IMPORTANT]
+> Espressif considers espflash and cargo-espflash to be feature-complete at this time. This does not mean we will stop maintaining them; contributions are still welcome. However, we do not plan to pursue further development at this point in time.
+
+
 ## [cargo-espflash](./cargo-espflash/)
 
 A cargo extension for flashing Espressif devices.