Function isBigint

isBigint(u: unknown): u is bigint
Type guard that checks if a value is a bigint.

Type Narrowing Behavior:
- Narrows unknown to bigint when true
- Identifies values created with BigInt() constructor or n suffix
Parameters
- u: unknown
  The value to check
Returns u is bigint
true if u is a bigint, false otherwise. When true, TypeScript narrows the type to bigint.
Example
```
const values: unknown[] = [1n, 2, 3n];

const bigints = values.filter(isBigint);

assert.deepStrictEqual(bigints, [1n, 3n]);
```
- Defined in src/guard/is-type.mts:175