add example for default account states

tokens/token-2022/default-account-state/native/README.md

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+## Token22 with default account state
+
+This extension makes it possible to set a default state for all underlying Token accounts of a certain Mint.
+
+These account states can be:
+
+- initialized: normal token account that can perform actions like transfers
+- frozen: the owner of this token account will not be able to perform any actions with his token.