Add PowerSync technical guide link (#877)

add technical guide link

Author: MongoCaleb

source/sync/device-sync-deprecation.txt

@@ -48,6 +48,7 @@ For more information on migration, refer to the following:
 - `PowerSync Reference Architecture Guide (PDF) <https://cdn.bfldr.com/2URK6TO/as/v5cmphbnwbhqh89frg5c7xw/MongoDB__PowerSync_Reference_Architecture_Guide>`__
 - `Atlas Device Sync to PowerSync migration guide <https://docs.powersync.com/resources/migration-guides/mongodb-atlas>`__
 - :ref:`Tutorial: Migrate a React Native Application from Device Sync to PowerSync <react_native-powersync>` 
+- `PowerSync DevRel Technical Guide <https://cdn.bfldr.com/2URK6TO/as/w44tjbkg7xkqz9m87kbw96b/PowerSync_DevRel_Technical_Guide>`__
 
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