feat(isEmail): add host_blacklist option

[fedeci]

We add an option to allow the user to exclude some specific domains from isEmail validation.
Fixes #1639

Checklist

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

[codecov]

Codecov Report

Merging #1641 (ac4896c) into master (05ceb18) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master     #1641   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          100       100           
  Lines         1847      1849    +2     
=========================================
+ Hits          1847      1849    +2     

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

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 05ceb18...ac4896c. Read the comment docs.

[tux-tn]

A little suggestion, we have a similar option in isURL called host_whitelist and host_blacklist that accepts hosts and regexes. What do you think about matching that behaviour to have consistency between validators options?

[fedeci]

It makes sense but I would keep the denylist instead of blacklist to use an inclusive language at least in new options.

I have nothing against blacklist and whitelist, but someone may be offended by such terms.

[tux-tn]

It makes sense but I would keep the denylist instead of blacklist to use an inclusive language at least in new options.

I have nothing against blacklist and whitelist, but someone may be offended by such terms.

Project maintainer views on this matter have already been shared here #1522

[fedeci]

It's always a good time to change your mind 🤷‍♂️

[fedeci]

Ping?

[tux-tn]

LGTM 🎉
Sorry for the long review delay, i missed the notification about new commits in this PR !

[profnandaa]

LGTM, thanks!