Refactor documentation structure and dependencies for migration to Fumadocs

- Updated `.gitignore` to include new build and generated content directories.
- Removed outdated Mintlify configuration files and documentation.
- Introduced new `MIGRATION.md` to outline the transition from Mintlify to Fumadocs.
- Added `mdx-components.tsx` for MDX component configuration and compatibility.
- Updated `package.json` and `next.config.mjs` for new dependencies and Next.js configuration.
- Created `source.config.ts` for content source configuration.
- Added OpenAPI specification in `openapi.json` for API documentation.
- Removed legacy files and adjusted project structure to align with Fumadocs conventions.

docs/lib/source.ts

@@ -0,0 +1,27 @@
+import { docs } from '@/.source';
+import { type InferPageType, loader } from 'fumadocs-core/source';
+import { lucideIconsPlugin } from 'fumadocs-core/source/lucide-icons';
+
+// See https://fumadocs.dev/docs/headless/source-api for more info
+export const source = loader({
+  baseUrl: '/docs',
+  source: docs.toFumadocsSource(),
+  plugins: [lucideIconsPlugin()],
+});
+
+export function getPageImage(page: InferPageType<typeof source>) {
+  const segments = [...page.slugs, 'image.png'];
+
+  return {
+    segments,
+    url: `/og/docs/${segments.join('/')}`,
+  };
+}
+
+export async function getLLMText(page: InferPageType<typeof source>) {
+  const processed = await page.data.getText('processed');
+
+  return `# ${page.data.title}
+
+${processed}`;
+}