Enhance form configuration with optional default styles

- Updated the `initForm` function to conditionally inject default styles based on the new `useDefaultStyles` configuration option.
- Added documentation for the `useDefaultStyles` property in the `FormConfig` interface, allowing users to customize styling behavior.

These changes provide greater flexibility for users to manage form styling according to their needs.

Author: lpssformspree

packages/formspree-ajax/src/form.ts

@@ -422,7 +422,9 @@ const injectDefaultStyles = (): void => {
 export const initForm = <T extends FieldValues = FieldValues>(
   config: FormConfig<T>
 ): FormHandle => {
-  injectDefaultStyles();
+  if (config.useDefaultStyles !== false) {
+    injectDefaultStyles();
+  }
 
   if (!config.formElement) {
     throw new Error('You must provide a `formElement` in the config');

packages/formspree-ajax/src/types.ts

@@ -144,6 +144,13 @@ export interface FormConfig<T extends FieldValues = FieldValues> {
    */
   debug?: boolean;
 
+  /**
+   * When true, injects default CSS styles for error messages, success banners,
+   * invalid field borders, and the loading spinner. Set to `false` to provide
+   * your own styles. Defaults to `true`.
+   */
+  useDefaultStyles?: boolean;
+
   /**
    * Callback invoked when the form is initialized.
    * @param context - The form context containing form element and configuration.