add changelog and upgrading doc

CHANGELOG.md

@@ -167,6 +167,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 
 ### API Breaking Changes
 
+* (store) [14746](https://github.com/cosmos/cosmos-sdk/pull/14746) Extract Store in its own go.mod and rename the package to `cosmossdk.io/store`.
 * (x/simulation) [#14751](https://github.com/cosmos/cosmos-sdk/pull/14751) Remove the `MsgType` field from `simulation.OperationInput` struct.
 * (crypto/keyring) [#13734](https://github.com/cosmos/cosmos-sdk/pull/13834) The keyring's `Sign` method now takes a new `signMode` argument. It is only used if the signing key is a Ledger hardware device. You can set it to 0 in all other cases.
 * (x/evidence) [14724](https://github.com/cosmos/cosmos-sdk/pull/14724) Extract Evidence in its own go.mod and rename the package to `cosmossdk.io/x/evidence`.

UPGRADING.md

@@ -41,6 +41,11 @@ The `gogoproto.goproto_stringer = false` annotation has been removed from most p
 
 References to `types/store.go` which contained aliases for store types have been remapped to point to appropriate  store/types, hence the `types/store.go` file is no longer needed and has been removed.
 
+##### Extract Store to a standalone module
+
+The `store` module is extracted to have a separate go.mod file which allows it be a standalone module. 
+All the store imports are now renamed to use `cosmossdk.io/store` instead of `github.com/cosmos/cosmos-sdk/store` across the SDK.
+
 ### SimApp
 
 #### Module Assertions
@@ -68,7 +73,7 @@ By default, the new `ProposalCancelRatio` parameter is set to 0.5 during migrati
 ##### Extract evidence to a standalone module
 
 The `x/evidence` module is extracted to have a separate go.mod file which allows it be a standalone module. 
-All the evidence imports are now renamed to use `cosmossdk.io/evidence` instead of `github.com/cosmos/cosmos-sdk/x/evidence` across the SDK.
+All the evidence imports are now renamed to use `cosmossdk.io/x/evidence` instead of `github.com/cosmos/cosmos-sdk/x/evidence` across the SDK.
 
 #### `x/nft`