feat: use custom llamaparse client to reduce bundle size

[JacobLinCool]

This pull request introduces several changes to the project, including adding new dependencies, refactoring the PDF parsing functionality, and adding tests for the new LlamaParse class. The most important changes are summarized below:

Dependencies and Configuration:

• Added vitest as a new testing framework in package.json.
• Added @sveltejs/adapter-vercel as a new adapter in package.json.
• Removed llamaindex from dependencies in package.json.
• Updated the Svelte adapter to use @sveltejs/adapter-vercel in svelte.config.js.

PDF Parsing Refactor:

• Created a new LlamaParse class in src/lib/server/llamaparse.ts to handle file parsing, status checking, and result retrieval.
• Refactored pdf2Text function in src/lib/server/pdf.ts to use the new LlamaParse class.

Testing:

• Added a new test suite for LlamaParse in tests/llamaparse.test.ts, including tests for PDF file parsing.

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src/lib/server/llamaparse.ts:45

• [nitpick] The error message could be more descriptive. Consider including additional context about the failure, such as the job ID.

throw new Error(`Parsing failed: ${status.error}`);