Add Igbo proper noun template

The template was provided by [[User:EnaldoSS]] [1] and
[[User:Tochiprecious]] [2] at [[Wikidata:Wikidata Lexeme Forms/Igbo]]
[3] – thank you!

[1]: https://www.wikidata.org/wiki/User:EnaldoSS
[2]: https://www.wikidata.org/wiki/User:Tochiprecious
[3]: https://www.wikidata.org/wiki/Wikidata:Wikidata_Lexeme_Forms/Igbo