feat: add ledger user guide for interlay app

Signed-off-by: Gregory Hill <[email protected]>

Author: gregdhill

docs/_assets/img/ledger/interlay/add-device.png

@@ -15,6 +15,7 @@
   * [Tokenomics](interlay/tokenomics.md)
   * [Governance](interlay/governance.md)
   * [Use iBTC](interlay/earn-with-ibtc.md)
+  * [Ledger](interlay/ledger.md)
 
 * **Kintsugi Canarynet**
 

docs/_assets/img/ledger/interlay/extrinsic.png

@@ -0,0 +1,34 @@
+# Ledger (WIP)
+
+## User Guide
+
+!> Make sure the Interlay app is open on your Ledger device!
+
+1. Open the [Polkadot-JS Apps UI](https://polkadot.js.org/apps/?rpc=wss%3A%2F%2Fapi.interlay.io%2Fparachain#/explorer) on the Interlay network
+2. Go to the "Settings" tab and select the option "Attach Ledger via WebUSB" for "manage hardware connections". Click "Save" to keep your settings.
+3. Go to the "Account" tab and you will see a new button that says "Add via Ledger". Click it.
+4. Set your account name, and choose the account type and address index. (You should now be able to find a new account with the type "ledger")
+
+![Add Device](../_assets/img/ledger/interlay/add-device.png)
+
+### Address
+
+You can verify a public address on the Ledger device by clicking "Show address on hardware device".
+
+![Show Address](../_assets/img/ledger/interlay/show-address.png)
+
+### Transactions
+
+Go to the "Extrinsics" tab and craft the "Submission". Supported calls are listed [here](https://github.com/Zondax/ledger-interlay#tokens).
+
+![Extrinsic](../_assets/img/ledger/interlay/extrinsic.png)
+
+Click the "Submit Transaction" button.
+
+![Submit](../_assets/img/ledger/interlay/submit.png)
+
+The app will now display the transaction information, review this and then "REJECT" to cancel or "APPROVE" to sign.
+
+## Developers
+
+Follow the build instructions specified [here](https://github.com/Zondax/ledger-interlay).