Fix multiple typos in sentence

- Add a missing 'a'
- Fix spelling of 'maintaining'

Author: tcharding

07_3_Integrating_with_Hardware_Wallets.md

@@ -4,7 +4,7 @@
 
 One of the greatest powers of PSBTs is the ability to hand transactions off to hardware wallets. This will be a great development tool for you if you continue to program with Bitcoin. However, you can't test it out now if you're using one of the configurations we suggest for this course — a VM on Linode per [§2.1](https://github.com/BlockchainCommons/Learning-Bitcoin-from-the-Command-Line/blob/master/02_1_Setting_Up_a_Bitcoin-Core_VPS_with_StackScript.md) or an even more farflung option such an AWS per [§2.2](https://github.com/BlockchainCommons/Learning-Bitcoin-from-the-Command-Line/blob/master/02_2_Setting_Up_Bitcoin_Core_Other.md) — because obviously you won't have any way to hook a hardware wallet up to your remote, virtual machine.
 
-> :book: ***What is a Hardware Wallet?*** A hardware wallet is an electronic device that improves the security of cryptocurrency by maintaing all the private keys on the device, rather than ever putting them on a computer directly connected to the internet. Hardware wallets have specific protocols for providing online interactions, usually managed by a program talking to the device through a USB port. In this chapter, we'll be managing a hardware wallet with `bitcoin-cli` and the `hwy.py` program.
+> :book: ***What is a Hardware Wallet?*** A hardware wallet is an electronic device that improves the security of a cryptocurrency by maintaining all the private keys on the device, rather than ever putting them on a computer directly connected to the internet. Hardware wallets have specific protocols for providing online interactions, usually managed by a program talking to the device through a USB port. In this chapter, we'll be managing a hardware wallet with `bitcoin-cli` and the `hwy.py` program.
 
 You have three options for moving through this chapter on hardware wallets: (1) read along without testing the code; (2) install Bitcoin on a local machine to fully test these commands; or (3) skip straight ahead to [Chapter 8: Expanding Bitcoin Transactions in Other Ways](08_0_Expanding_Bitcoin_Transactions_Other.md). We suggest option #1, but if you really want to get your hands dirty we'll also give some support for #2 by talking about using a Macintosh (a hardware-platform supported by [Bitcoin Standup](https://github.com/BlockchainCommons/Bitcoin-Standup)) for testing.