In currency.md API link does't Work

# The url for currency exchange API is changed 
## From
```
https://cdn.jsdelivr.net/gh/fawazahmed0/currency-api@1/latest/currencies/${currency}.json
```
 ## To
``` 
https://cdn.jsdelivr.net/npm/@fawazahmed0/currency-api@latest/v1/currencies/${currency}.json
 ```