Add support for sqlite-vec vector store

[davidmigloz]

LangChain resources:

• https://python.langchain.com/v0.2/docs/integrations/providers/sqlite
• https://python.langchain.com/v0.2/docs/integrations/vectorstores/sqlitevss/

Dart resources:

• https://github.com/asg017/sqlite-vec
• https://github.com/simolus3/sqlite3.dart

Example:

• https://github.com/rodydavis/flutter_sqlite_document_search

Blocking issue on web:

• Compiling a sqlite extension for wasm and ffi simolus3/sqlite3.dart#247

[Heinrich-vanNieuwenhuizen]

Hi @davidmigloz , you can assign this to me

[Heinrich-vanNieuwenhuizen]

awaiting a review on #569
@davidmigloz

[davidmigloz]

Thanks for the work @Heinrich-vanNieuwenhuizen! 🙌
I'll review it soon.