new validator: isMailtoURI, validate the mailto link URI format

[uksarkar]

Added a new validation method for validating the mailto: link URI. Where it'll validate the URI format and also the email provided inside the appropriate query params.

Here is the format of a mailto link URI mailto:to(optional, comma-separated emails)?cc=(optional, comma-separated emails)&bb=(optional, comma-separated emails)&subject=(optional)&body=(optional)

Some links:
https://mailtrap.io/blog/mailto-links-explained/
https://en.wikipedia.org/wiki/Mailto

Checklist

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

[codecov]

Codecov Report

Base: 100.00% // Head: 99.95% // Decreases project coverage by -0.05% ⚠️

Coverage data is based on head (49a2e12) compared to base (43803c0).
Patch coverage: 97.67% of modified lines in pull request are covered.

❗ Current head 49a2e12 differs from pull request most recent head 21fc562. Consider uploading reports for the commit 21fc562 to get more accurate results

Additional details and impacted files

@@             Coverage Diff             @@
##            master    #2188      +/-   ##
===========================================
- Coverage   100.00%   99.95%   -0.05%     
===========================================
  Files          106      107       +1     
  Lines         2348     2391      +43     
  Branches       593      605      +12     
===========================================
+ Hits          2348     2390      +42     
- Partials         0        1       +1     

Impacted Files	Coverage Δ
src/lib/isMailtoURI.js	97.61% <97.61%> (ø)
src/index.js	100.00% <100.00%> (ø)

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[WikiRik]

Could you provide some use cases for this new validator? When would an user need to input such a mailto URI? Or when would you want to check this coming from another system? I think this would be a too niche use case for this project

[uksarkar]

Could you provide some use cases for this new validator? When would an user need to input such a mailto URI? Or when would you want to check this coming from another system? I think this would be a too niche use case for this project

For projects like website builder, it would be great to provide the user some feedback about what they are trying to achieve and whether it's valid or not.

[profnandaa]

LGTM, thanks for your contrib! 🎉