Make CLI docstrings / metadata render well in both `--help` and generated md file

[georgeh0]

With #1084 we start to generate markdown from docstrings / metadata from python/cocoindex/cli.py.
Since when we create the CLI, we didn't have the auto generated md yet, something aren't rendered very well.

For examples:

• Something should be backquoted, like APP_FLOW_SPECIFIER and an_installed.module_name in

  cocoindex/docs/docs/core/cli-commands.md

  Lines 38 to 48 in 624b233

  	APP_FLOW_SPECIFIER: Specifies the application and optionally the target flow.
  	Can be one of the following formats:
  	- path/to/your_app.py
  	- an_installed.module_name
  	- path/to/your_app.py:SpecificFlowName
  	- an_installed.module_name:SpecificFlowName

• There're redundant blank lines that break up sentences into separate paragraphs:

  cocoindex/docs/docs/core/cli-commands.md

  Lines 74 to 80 in 624b233

  	If APP_TARGET (path/to/app.py or a module) is provided, lists flows defined
  	in the app and their backend setup status.
  	If APP_TARGET is omitted, lists all flows that have a persisted setup in the
  	backend.

Goal: make both --help and generated md look well.

To achieve this goal, we need to:

• Update python/cocoindex/cli.py
• The script to generate the markdown dev/generate_cli_docs.py may also need to be updated, e.g. avoid unnecessary blank lines.

To test it, you may

• Run cocoindex --help, cocoindex <subcommand> --help
• View the generated markdown, by
  • Run dev/generate_cli_docs.py
  • Also view the generated markdown in docusaurus by following docs/README.md

[S3lc0uth]

Please assign it

[georgeh0]

@S3lc0uth assigned. Thanks for taking this!