docs: Document rofl top-up command

Author: matevz

docs/rofl.md

@@ -194,6 +194,19 @@ offer:
 
 [ROFL marketplace]: https://github.com/oasisprotocol/oasis-sdk/blob/main/docs/rofl/features/marketplace.mdx
 
+## Top-up payment for the machine {#top-up}
+
+Run `rofl machine top-up` to extend the rental of the machine obtained from
+the [ROFL marketplace]. The rental is extended under the terms of the original
+offer. Specify the extension period with [`--term`][term-flags] and
+[`--term-count`][term-flags] parameters.
+
+![code shell](../examples/rofl/machine-top-up.in.static)
+
+![code](../examples/rofl/machine-top-up.out.static)
+
+[term-flags]: #deploy
+
 ## Advanced
 
 ### Upgrade ROFL app dependencies {#upgrade}

examples/rofl/machine-top-up.in.static

@@ -0,0 +1 @@
+oasis rofl machine top-up --term hour --term-count 12

examples/rofl/machine-top-up.out.static

@@ -0,0 +1,34 @@
+Using provider:     oasis1qp2ens0hsp7gh23wajxa4hpetkdek3swyyulyrmz (oasis1qp2ens0hsp7gh23wajxa4hpetkdek3swyyulyrmz)
+Top-up machine:     default [000000000000022a]
+Top-up term:        12 x hour
+Unlock your account.
+? Passphrase: 
+You are about to sign the following transaction:
+Format: plain
+Method: roflmarket.InstanceTopUp
+Body:
+  {
+    "provider": "oasis1qp2ens0hsp7gh23wajxa4hpetkdek3swyyulyrmz",
+    "id": "000000000000022a",
+    "term": 1,
+    "term_count": 12
+  }
+Authorized signer(s):
+  1. AyZKkxNFeyqLI5HGTYqEmCcYxKGo/kueOzSHzdnrSePO (secp256k1eth)
+     Nonce: 996
+Fee:
+  Amount: 0.0013614 TEST
+  Gas limit: 13614
+  (gas price: 0.0000001 TEST per gas unit)
+
+Network:  testnet
+ParaTime: sapphire
+Account:  dave
+? Sign this transaction? Yes
+(In case you are using a hardware-based signer you may need to confirm on device.)
+Broadcasting transaction...
+Transaction included in block successfully.
+Round:            12917124
+Transaction hash: 094ddc21c39acd96789153003016bda5d2a0077e7be11635bb755b6c49c287ac
+Execution successful.
+Machine topped up.