[+]: fixed for "Stringy" v2.1

[~]: removed unused variable from "UTF8::str_ireplace()"

[*]: fixed typo in comment

[+]: "Handle the third argument of mb_convert_encoding() being an arr…

…ay." | thx @leofeyer

-> https://github.com/leofeyer/utf8/commit/3eae06657b1b88217d5c9a783ab8b7ac4117bdb3
-> https://github.com/leofeyer/utf8/commit/7c33314c1eb8796f11ddfaf38a1b114568792359
-> https://github.com/leofeyer/utf8/commit/7b9892a0f3fd919e01b39401b7f20e29ea1ac8d1

Revert "Revert "Revert "[~]: optmized "UTF8::html_entity_decode()""""

This reverts commit 8272c1e.

[+]: use "str_replace()" instead of "strtr()" [performance]

[+]: decode utf-8 codepoints

Merge remote-tracking branch 'origin/master'

* origin/master:
  Applied fixes from StyleCI

[+]: added test for "UTF8::str_ireplace()"

[+]: optimize "UTF8::str_ireplace()" v2