fix(editor): handle footnote reference immediately follow URLs when importing markdown (#12449)

Closes: [BS-3525](https://linear.app/affine-design/issue/BS-3525/markdown-adapter-紧跟着链接的-footnote-reference-会被识别成链接的一部分)

<!-- This is an auto-generated comment: release notes by coderabbit.ai -->

## Summary by CodeRabbit

- **New Features**
  - Improved handling of footnote references that immediately follow URLs in markdown, ensuring correct spacing and parsing.
- **Bug Fixes**
  - Footnote references after URLs are now parsed correctly, preventing formatting issues.
- **Tests**
  - Added comprehensive test suites to verify footnote reference preprocessing and markdown conversion.
- **Chores**
  - Introduced Vitest as a development dependency and added a dedicated test configuration for the footnote module.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

blocksuite/affine/inlines/footnote/vitest.config.ts

@@ -0,0 +1,25 @@
+import { defineConfig } from 'vitest/config';
+
+export default defineConfig({
+  esbuild: {
+    target: 'es2018',
+  },
+  test: {
+    browser: {
+      enabled: true,
+      headless: true,
+      name: 'chromium',
+      provider: 'playwright',
+      isolate: false,
+      providerOptions: {},
+    },
+    include: ['src/__tests__/**/*.unit.spec.ts'],
+    testTimeout: 500,
+    coverage: {
+      provider: 'istanbul',
+      reporter: ['lcov'],
+      reportsDirectory: '../../../.coverage/footnote',
+    },
+    restoreMocks: true,
+  },
+});