Add upgrade instruction

app/upgrades/v0_1_2/README.md

@@ -0,0 +1,26 @@
+# Upgrade to v0.1.2
+
+## Guide for Upgrading from v0.1.1 to v0.1.2
+
+1. Halt the currently running `galacticad` process.
+2. Fetch the latest updates from the repository and switch to the `v0.1.2` tag.
+    ```bash
+    git fetch --all --tags
+    git checkout v0.1.2
+    ```
+3. Build the updated source code.
+    ```bash
+    make install
+    ```
+4. Execute the upgrade script located at ./scripts/upgrade_v0_1_2.sh
+    ```bash
+    ./scripts/upgrade_v0_1_2.sh
+    ```
+   Ensure the following environment variable is defined:
+    - `GALACTICA_HOME`: Specifies the home directory for the `galacticad` node.
+
+   The script executes the following operations:
+    - Updates the node storage to version v0.1.2.
+    - Reverts the state of the latest block.
+    - Creates a backup of the current priv_validator_state.json and replaces it with a new version with default settings.
+5. Restart the `galacticad` node.