chore: Move Falsy, Primitive to basic directory

source/basic/Falsy.d.ts

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+/**
+ * A type representing all the values that are considered falsy in JavaScript.
+ *
+ * In JavaScript, falsy values are those that evaluate to `false` in a Boolean context.
+ * This type includes:
+ *
+ * - `false` : The Boolean false value.
+ * - `''` : An empty string.
+ * - `0`: The number zero.
+ * - `null`: The null value representing the absence of any value.
+ * - `undefined`: A value that indicates a variable has not been assigned a value.
+ *
+ * This type can be useful for defining variables, parameters, or return types that
+ * should only accept or return falsy values.
+ */
+
+export type Falsy = false | '' | 0 | null | undefined;

source/basic/index.d.ts

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+export type { Falsy } from './Falsy';
+export type { Primitive } from './Primitive';

source/index.d.ts

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+export * from './basic';