breaking changes: Add a CHANGES.md file with details of the recent breaking changes

Author: shahpiyushv

CHANGES.md

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+Here is a list of changes which can break your existing code based on ESP Jumpstart.
+
+### Factory NVS variables changed from string to blob encoding type.
+
+*commit 4fbc0560df16b82b12b86dc1e13436ffce7cac06*
+
+7\_mfg/mfg\_config.csv now uses NVS blobs instead of strings since NVS strings cannot
+be larger than 1984 bytes. In some cases the certificate size can go beyond this number.
+
+### conn\_mgr\_prov : API changes for more clarity, flexibility and control
+
+*commit ff311c666a24ccb0fffa06da399f016fce66bd7e*
+    
+List of changes :
+
+* new APIs:
+  * `conn_mgr_prov_config_t` : Configuration structure for specifying:
+    * the provisioning `scheme` of type `conn_mgr_prov_scheme_t` which has 2 ready to use values:
+      * `conn_mgr_prov_scheme_ble` : for provisioning over BLE transport + GATT server
+      * `conn_mgr_prov_scheme_softap` : for provisioning over SoftAP transport + HTTP server
+    * `scheme_event_handler` for specifying an event handler which may be required for conditioning the state of the program prior to starting the user app after provisioning is complete. When using `conn_mgr_prov_scheme_ble` one can choose one of the following available scheme specific handlers :
+      * `CMP_EVENT_HANDLER_NONE` : No scheme specific event handling
+      * `CMP_SCHEME_BLE_EVENT_HANDLER_FREE_BTDM` : Free BT/BLE memory (when user app doesn't require these after provisioning is over)
+      * `CMP_SCHEME_BLE_EVENT_HANDLER_FREE_BT` : Free only BT memory (when user app requires BLE to function even after provisioning is over)
+      * `CMP_SCHEME_BLE_EVENT_HANDLER_FREE_BLE` : Free only BLE memory (when user app requires BT to function)
+    * `app_event_handler` for specifying application specific event handler
+  * `conn_mgr_prov_init()` : For initializing the manager with a specified configuration
+  * `conn_mgr_prov_wait()` : Blocking wait for provisioning to complete
+  * `conn_mgr_prov_deinit()` : For de-initializing the manager and freeing its resources
+  * `conn_mgr_prov_stop_provisioning()` : For stopping an active provisioning service
+* modified APIs:
+  * `conn_mgr_prov_start_provisioning()` : Doesn't accept prov_type anymore. Instead the mode (BLE/SoftAP) is configured during init
+  * `conn_mgr_prov_event_handler()` : Returns error when provisioning is not running
+  * `conn_mgr_prov_t` rename to `conn_mgr_prov_scheme_t`
+  * `conn_mgr_prov_mode_ble` rename to `conn_mgr_prov_scheme_ble`
+  * `conn_mgr_prov_mode_softap` renamed to `conn_mgr_prov_scheme_softap`
+  * Macros with prefix `CM_*` renamed to that with prefix `CMP_*`
+* Examples `4_network_config`, `5_cloud`, `6_ota` and `7_mfg` modified as per new APIs. Releasing of BT/BLE memory pre/post provisioning is taken care of by manager as scheme handler `CMP_SCHEME_BLE_EVENT_HANDLER_FREE_BTDM` is used, even in the case when provisioning is not started. If provisioning service is started, de-initialization is triggered by the application specific event handler `prov_event_handler()` after provisioning finishes. This frees the main app from the burden of waiting for provisioning to finish and then calling manager de-init.

README.md

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+> If you have already been using ESP Jumpstart, please have a look at some breaking [Changes](CHANGES.md).
+
 ESP-Jumpstart
 =============
 [[中文]](./README_cn.md)