feat: Add getPhoneCodesForWilaya

[joeylnguyen]

Description

• Added getPhoneCodesForWilaya method that returns an array of phone codes for a given wilaya code
• Added tests for getPhoneCodesForWilaya
• Exported method in index.js
• Updated tests for index.js
• Updated README

References #19

Type of change

• [x] New feature (non-breaking change which adds functionality)

Checklist:

• [x] I checked that there's no dataset update (can be done by running npm run update-dataset)
• [x] npm test passes on my machine
• [x] npm run lint passes on my machine

[joeylnguyen]

@Fcmam5 I plan on submitting a separate PR for getPhoneCodeForWilaya. Do you agree with that, or would you rather I add that feature to this PR?

[Fcmam5]

@Fcmam5 I plan on submitting a separate PR for getPhoneCodeForWilaya. Do you agree with that, or would you rather I add that feature to this PR?

@joeylnguyen It's fine to submit it in a separate PR 😄 , this will make review easier for us.
Let's just mention that they're both related #19

Happy Hacking !

[Fcmam5]

@all-contributors add @joeylnguyen for code 😃

[allcontributors[bot]]

@Fcmam5

I've put up a pull request to add @joeylnguyen! :tada: