feat(isAlpha, isAlphanumeric): Added support for Bengali language

[rak810]

• feat(isAlpha, isAlphanumeric): Added support for Bengali language
• Made some changes in alpha.js according to npm test results
• Written tests for Bengali language features in isAlpha and is Alpha

Checklist

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

[codecov]

Codecov Report

Merging #1678 (74ea0fb) into master (3873ebf) will not change coverage.
The diff coverage is 100.00%.

❗ Current head 74ea0fb differs from pull request most recent head c7c0760. Consider uploading reports for the commit c7c0760 to get more accurate results

@@            Coverage Diff             @@
##            master     #1678    +/-   ##
==========================================
  Coverage   100.00%   100.00%            
==========================================
  Files          104       101     -3     
  Lines         2120      1860   -260     
  Branches       475         0   -475     
==========================================
- Hits          2120      1860   -260     

Impacted Files	Coverage Δ
src/lib/alpha.js	100.00% <100.00%> (ø)
src/index.js	100.00% <0.00%> (ø)
src/lib/isIP.js	100.00% <0.00%> (ø)
src/lib/isIn.js	100.00% <0.00%> (ø)
src/lib/trim.js	100.00% <0.00%> (ø)
src/lib/isBIC.js	100.00% <0.00%> (ø)
src/lib/isEAN.js	100.00% <0.00%> (ø)
src/lib/isHSL.js	100.00% <0.00%> (ø)
src/lib/isInt.js	100.00% <0.00%> (ø)
... and 84 more

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[profnandaa]

LGTM, thanks for your contrib! 🎉
/cc. @ezkemboi @tux-tn -- please have a second look.

[tux-tn]

Hello @rak810 Can you please fix merge conflicts?

addressed