fix: typos in adjectives (tomalaforge#1010)

Also, add a bit more explanation

Author: LMFinney

apps/signal/54-pipe-observable-to-signal/src/app/currency.service.ts

@@ -10,9 +10,9 @@ export interface Currency {
 export const currency: Currency[] = [
   { name: 'Euro', code: 'EUR', symbol: '€' },
   { name: 'Dollar US', code: 'USD', symbol: 'US$' },
-  { name: 'Dollar Autralien', code: 'AUD', symbol: 'AU$' },
-  { name: 'Livre Sterling', code: 'GBP', symbol: '£' },
-  { name: 'Dollar Canadien', code: 'CAD', symbol: 'CAD' },
+  { name: 'Dollar Australian', code: 'AUD', symbol: 'AU$' },
+  { name: 'Pound Sterling', code: 'GBP', symbol: '£' },
+  { name: 'Dollar Canadian', code: 'CAD', symbol: 'CAD' },
 ];
 
 @Injectable()

docs/src/content/docs/challenges/signal/54-pipe-observable-to-signal.md

@@ -4,6 +4,7 @@ description: Challenge 54 is about refactoring an application using observable t
 author: thomas-laforge
 contributors:
   - tomalaforge
+  - LMFinney
 challengeNumber: 54
 command: signal-pipe-observable-to-signal
 sidebar:
@@ -17,6 +18,6 @@ We have a legacy application that is using observables to store a state. Signals
 
 ## Statement
 
-So the goal of this challenge is to refactor the following application to be a fully signal based application.
+So, the goal of this challenge is to refactor the following application to be a fully signal-based application. When you are done, neither the pipe nor the service should import RxJS.
 
-Be careful along the way, everything might not work as you wish.
+Be careful along the way; everything might not work as you wish.