### What problem does this PR solve?
#474 

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

parse markdown files as txt

### What problem does this PR solve?

support markdown files

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

### What problem does this PR solve?

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

### What problem does this PR solve?

#384

### Type of change

- [x] Performance Improvement

### What problem does this PR solve?

Issue link:#384
### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

### What problem does this PR solve?

_Briefly describe what this PR aims to solve. Include background context
that will help reviewers understand the purpose of the PR._

Issue link:#[[Link the issue
here](https://github.com/infiniflow/ragflow/issues/236)]

### Type of change

- [x] Documentation Update

### What problem does this PR solve?

_Briefly describe what this PR aims to solve. Include background context
that will help reviewers understand the purpose of the PR._

Issue link:#[[Link the issue
here](https://github.com/infiniflow/ragflow/issues/226)]

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

* add use layout or not option

* trival

* fix position extraction bug

* remove delimiter for naive parser

* init README of deepdoc, add picture processer.

* add resume parsing

Add naive chunking method to RAG