docs(arktype-utils): Adds README (#6)

Author: jhechtf

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+.changeset/**/*.md

packages/arktype-utils/README.md

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+# Arktype Utils
+
+[ArkType](https://www.npmjs.com/package/arktype) is a TypeScript validator that delivers highly optimized validators.
+
+I created some wrappers around ArkType's validators.
+
+**_This is still an early version, the shape might change. I will attempt to keep a nice deprecation path._**
+
+## Turning FormData into an object
+
+This is a helper method, primarily for Node-based backends that need to turn `FormData` values into a JS object.
+
+**NOTE**: This does _no_ validation, it just turns the values into an object
+
+```ts
+import { formDataToObject } from '@jhecht/arktype-utils';
+
+const fd = new FormData();
+fd.append('name', 'Bob');
+fd.append('surname', 'Surbob');
+fd.append('age', '31');
+
+const obj = formDataToObject(fd);
+```
+
+For repeated entries, if there is more than 1 value found, it will be turned into an array
+
+```ts
+import { formDataToObject } from '@jhecht/arktype-utils';
+const fd = new FormData();
+fd.append('name', 'Bob');
+fd.append('name', 'John');
+
+const obj = formDataToObject(fd);
+
+// { name: ['Bob', 'John']}
+console.info(obj);
+```
+
+This method all does it's best guess for JSON-parsible values, including BigInt
+
+```ts
+import { formDataToObject } from '@jhecht/arktype-utils';
+
+const fd = new FormData();
+fd.append('number', '13');
+fd.append('otherNumber', '3.1415');
+fd.append('bigNumber', '300n');
+
+const obj = formDataToObject(fd);
+
+// { number: 13, otherNumber: 3.1415, bigNumber: 300n } -- no strings!
+console.info(obj);
+```
+
+You can also for an element to _always_ be an array by ending it with `[]`:
+
+```ts
+import { formDataToObject } from '@jhecht/arktype-utils';
+
+const fd = new FormData();
+fd.append('email[]', 'bob@bob.bob');
+
+const obj = formDataToObject(fd);
+
+// { email: ['bob@bob.bob'] }
+console.info(obj);
+```
+
+## Validating Data with ArkType
+
+I created this wrapper, which `throws` if there are any `error` values. It takes two arguments, one being a `FormData` object, and the other a `type` or `scope` call from ArkType, which serves as the validator for the object-ified `FormData`.
+
+```ts
+import { validateFormData } from '@jhecht/arktype-utils';
+import { type } from 'arktype';
+
+const fd = new FormData();
+// Assume `fd` is gotten from the request body here
+
+try {
+  const obj = validateFormData(
+    fd,
+    type({
+      name: 'string>=2',
+      age: '13<=number',
+      favoriteMovies: 'string[]',
+    }),
+  );
+  // If this code is ran we know that the value of the `fd` variables passes the above validations when turned into an object
+  console.info(obj);
+} catch (e) {
+  // If we end up here, `e` will be the `Problems` object returned by ArkType's validator
+  console.error(e);
+}
+```