Added isMobilePhone valid regex for 3 countries

[Mustafiz04]

I have added valid regex for Afghanistan, Yemen and Western Sahara.
I will add more regex for missing countries mainly Caribbean and small Island.
Solved and added test for issue #1761

Checklist

• PR contains only changes related; no stray files, etc.
• README updated (where applicable)
• Tests written (where applicable)

[codecov]

Codecov Report

Merging #1925 (fba9680) into master (c193fe5) will not change coverage.
The diff coverage is n/a.

❗ Current head fba9680 differs from pull request most recent head afdbd68. Consider uploading reports for the commit afdbd68 to get more accurate results

@@            Coverage Diff            @@
##            master     #1925   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          104       102    -2     
  Lines         2120      2072   -48     
  Branches       475       472    -3     
=========================================
- Hits          2120      2072   -48     

Impacted Files	Coverage Δ
src/lib/isMobilePhone.js	100.00% <ø> (ø)
src/index.js	100.00% <0.00%> (ø)
src/lib/isIP.js	100.00% <0.00%> (ø)
src/lib/alpha.js	100.00% <0.00%> (ø)
src/lib/isURL.js	100.00% <0.00%> (ø)
src/lib/isTaxID.js	100.00% <0.00%> (ø)
src/lib/isBase32.js	100.00% <0.00%> (ø)
src/lib/isLength.js	100.00% <0.00%> (ø)
src/lib/isMagnetURI.js	100.00% <0.00%> (ø)
src/lib/isCreditCard.js	100.00% <0.00%> (ø)
... and 6 more

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[Mustafiz04]

@ezkemboi can you please review this PR ?

I apologise for being a little late for this PR because I was busy at work.
Could you please provide a place where I can learn regex because I'm having trouble developing regex for the Caribbean and tiny islands?

[rubiin]

Looks good

[rubiin]

Thankyou for the contribution 🎉