refactor: migrate reader type into core (#1111)

packages/core/src/schema/index.ts

packages/core/src/schema/type.ts

packages/llamaindex/src/ingestion/IngestionPipeline.ts

packages/llamaindex/src/readers/AssemblyAIReader.ts

packages/llamaindex/src/readers/CSVReader.ts

packages/llamaindex/src/readers/DiscordReader.ts

packages/llamaindex/src/readers/DocxReader.ts

packages/llamaindex/src/readers/HTMLReader.ts

packages/llamaindex/src/readers/ImageReader.ts

packages/llamaindex/src/readers/JSONReader.ts

packages/llamaindex/src/readers/LlamaParseReader.ts

packages/llamaindex/src/readers/MarkdownReader.ts

packages/llamaindex/src/readers/NotionReader.ts

packages/llamaindex/src/readers/PDFReader.ts

...ages/llamaindex/src/readers/SimpleDirectoryReader.edge.ts

packages/llamaindex/src/readers/SimpleDirectoryReader.ts

packages/llamaindex/src/readers/SimpleMongoReader.ts

packages/llamaindex/src/readers/TextFileReader.ts

packages/llamaindex/src/readers/type.ts