[Bug] Duplicate subheadings in v1.1 documentation

[joshuayao]

Please check the subheadings using the following links:

• https://opea-project.github.io/latest/microservices/index.html#retrievers-microservice
• https://opea-project.github.io/latest/microservices/index.html#lvms-microservice
• https://opea-project.github.io/latest/microservices/index.html#llms-microservice
• https://opea-project.github.io/latest/microservices/index.html#dataprep-microservice

[NeoZhangJianyu]

The root cause is the current online doc build principle will scan all of md files of a repo and list them in one page: index.html.
Some md files have same tile.

I create a PR as base to refactor the online doc: #267
After it's done, this issue will be resolved.

[yinghu5]

Remind：the doc team will handle it