[FEATURE]: `values()` should accept readonly values during `insert`.

### Describe what you want

The `insert(...).values()` call should accept a readonly object or array. My programming style is very readonly (which easily prevents a entire large category bugs), so not accepting readonly is really inconvenient for me.

I'd suggest replacing this:

```typescript
values(value: PgInsertValue): PgInsertBase;
values(values: PgInsertValue[]): PgInsertBase;
```

with something this:

```typescript
values(value: DeepReadonly>): PgInsertBase;
values(values: readonly DeepReadonly>[]): PgInsertBase;
```

using any of the `DeepReadonly` definitions, e.g. here's a good one from the package `ts-essentials`:

```typescript
export declare type Primitive = string | number | boolean | bigint | symbol | undefined | null;
export declare type Builtin = Primitive | Function | Date | Error | RegExp;
/** Like Readonly but recursive */
export declare type DeepReadonly = T extends Builtin
? T
: T extends Map
? ReadonlyMap, DeepReadonly>
: T extends ReadonlyMap
? ReadonlyMap, DeepReadonly>
: T extends WeakMap
? WeakMap, DeepReadonly>
: T extends Set
? ReadonlySet>
: T extends ReadonlySet
? ReadonlySet>
: T extends WeakSet
? WeakSet>
: T extends Promise
? Promise>
: T extends {}
? {
readonly [K in keyof T]: DeepReadonly;
}
: Readonly;
```