feat: improve typescript definition (#28)

This commit improves the typescript definition of `hashValue()` by introducing a generic type argument and an explicit return type. This ensures that the inferred return type of the function matches the type of values in the provided `options` array.

Before:
```ts
const options1 = [1, 2, 3];
const options2 = ['a', 'b', 'c'];
const options3 = ['a', 'b', 'c', 1, 2, 3];
const value1 = hashValue('str', options1); // tsc: type of `value1` is `unknown`
const value2 = hashValue('str', options2); // tsc: type of `value2` is `unknown`
const value3 = hashValue('str', options3); // tsc: type of `value3` is `unknown`
```

After:
```ts
const options1 = [1, 2, 3];
const options2 = ['a', 'b', 'c'];
const options3 = ['a', 'b', 'c', 1, 2, 3];
const value1 = hashValue('str', options1); // tsc: type of `value1` is `number`
const value2 = hashValue('str', options2); // tsc: type of `value2` is `string`
const value3 = hashValue('str', options3); // tsc: type of `value3` is `string | number`
```

src/index.ts

@@ -4,7 +4,7 @@
  * @param source String to hash.
  * @param options Collection of options to get value from.
  */
-export default function hashValue(source: string, options: unknown[]) {
+export default function hashValue<T>(source: string, options: T[]): T {
   let hash = 0;
 
   if (source.length === 0 || options.length === 0) {