docs: modify docs display & add images (#17575)

### Summary

modify docs display
add some images
delete enterprise docs
standardize capitalization

docs/develop/contributing.md

@@ -5,7 +5,7 @@ sidebar_custom_props: {
   categoryIcon: LucideBookA
 }
 ---
-# Contribution guidelines
+# Contribution Guidelines
 
 General guidelines for RAGFlow's community contributors.
 
@@ -16,7 +16,7 @@ This document offers guidelines and major considerations for submitting your con
 - To report a bug, file a [GitHub issue](https://github.com/infiniflow/ragflow/issues/new/choose) with us.
 - For further questions, you can explore existing discussions or initiate a new one in [Discussions](https://github.com/orgs/infiniflow/discussions).
 
-## What you can contribute
+## What You Can Contribute
 
 The list below mentions some contributions you can make, but it is not a complete list.
 
@@ -27,9 +27,9 @@ The list below mentions some contributions you can make, but it is not a complet
 - Updates to existing documents, codes, or annotations.
 - Suggesting more user-friendly error codes
 
-## File a pull request (PR)
+## File a Pull Request (PR)
 
-### General workflow
+### General Workflow
 
 1. Fork our GitHub repository.
 2. Clone your fork to your local machine:
@@ -42,18 +42,18 @@ The list below mentions some contributions you can make, but it is not a complet
 `git push origin my-branch.`
 6. Submit a pull request for review.
 
-### Before filing a PR
+### Before Filing a PR
 
 - Consider splitting a large PR into multiple smaller, standalone PRs to keep a traceable development history.
 - Ensure that your PR addresses just one issue, or keep any unrelated changes small.
 - Add test cases when contributing new features. They demonstrate that your code functions correctly and protect against potential issues from future changes.
 
-### Describing your PR
+### Describing Your PR
 
 - Ensure that your PR title is concise and clear, providing all the required information.
 - Refer to a corresponding GitHub issue in your PR description if applicable.
 - Include sufficient design details for *breaking changes* or *API changes* in your description.
 
-### Reviewing & merging a PR
+### Reviewing & Merging a PR
 
 Ensure that your PR passes all Continuous Integration (CI) tests before merging it.