inflection(Just for learning)

Inflection pluralizes and singularizes English nouns implemented by rust.

Copy from go version.

```rust use inflection::{singular, plural};

asserteq!(plural::<_, String>("person"), "people".tostring()); asserteq!(plural::<_, String>("Person"), "People".tostring()); asserteq!(plural::<_, String>("PERSON"), "PEOPLE".tostring()); asserteq!(plural::<_, String>("bus"), "buses".tostring()); asserteq!(plural::<_, String>("BUS"), "BUSES".tostring()); asserteq!(plural::<_, String>("Bus"), "Buses".tostring()); asserteq!(plural::<_, String>("FancyPerson"), "FancyPeople".tostring());

asserteq!(singular::<_, String>("people"), "person".tostring());
asserteq!(singular::<_, String>("PEOPLE"), "PERSON".tostring());
asserteq!(singular::<_, String>("buses"), "bus".tostring());
asserteq!(singular::<_, String>("People"), "Person".tostring());
asserteq!(singular::<_, String>("BUSES"), "BUS".tostring());
asserteq!(singular::<_, String>("Buses"), "Bus".tostring());
asserteq!(singular::<_, String>("FancyPeople"), "FancyPerson".tostring()); ```