Function singularize

singularize(word: string): string
Converts a plural word to its singular form using simple rules.
Parameters
- word: string
  The plural word to convert.
Returns string
The singular form of the word.
Since
1.1.0
Example
```
singularize("batteries"); // "battery"
singularize("boxes");     // "box"
singularize("cars");      // "car"
singularize("sheep");     // "sheep" (unchanged)
```
- Defined in string/singularize.ts:18