docs: add flow API overview

README.md

@@ -225,8 +225,8 @@ Make sure to continue with our [Jina 101 Guide](https://github.com/jina-ai/jina#
 
 <tr>
 <td>
-<h4>Using Flow API to Compose Your Search Workflow</h4>
-Learn how to blah blah blah with blah blah blah
+<h4>Using Flow API to Compose Your Jina Workflow</h4>
+Compose Pods to work together, either sequentially or in parallel; locally or remotely.  
 </td>
 <td><h3>🐣 </h3></td>
 </tr>

docs/chapters/flow/README.md

@@ -4,6 +4,7 @@ In a search system, task such as indexing is a workflow often involves multiple
 
 Flow API is a context manager for Pods. Each `Flow` object corresponds to a real-world task, it helps user to manage the states and contexts of all Pods required in that task. Flow API translates a workflow defined in Python code, YAML spec and interactive graph to a runtime backed by multi-thread/process, Kubernetes, Docker Swarm, etc. Users don't need to worry about where the Pod is running and how the Pods are connected.
 
+![Flow is a context manager](flow-api-doc.png)
 
 <!-- START doctoc generated TOC please keep comment here to allow auto update -->
 <!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->

docs/index.rst

@@ -23,6 +23,7 @@ Welcome to Jina Documentations!
 
    chapters/helloworld/main
    chapters/101/.sphinx
+   chapters/flow/README
    chapters/hub/main
    chapters/remote/main
    chapters/dashboard/main
@@ -33,8 +34,6 @@ Welcome to Jina Documentations!
    :caption: Developer Reference
 
    chapters/cli/main
-   chapters/all_exec
-   chapters/all_driver
    api/jina
    chapters/yaml/yaml
    chapters/proto/main
@@ -52,33 +51,35 @@ Welcome to Jina Documentations!
    :maxdepth: 2
    :caption: Contributing
 
-   chapters/CONTRIBUTING.md
+   chapters/CONTRIBUTING
    chapters/jep/main
 
 
 .. toctree::
    :maxdepth: 1
    :caption: Release Notes
 
-   chapters/RELEASE.md
-   chapters/CHANGELOG.md
+   chapters/RELEASE
+   chapters/CHANGELOG
 
 
 .. toctree::
    :maxdepth: 1
    :caption: Frequently Asked Questions
 
-   chapters/troubleshooting.md
+   chapters/troubleshooting
    chapters/faq/user
    chapters/faq/dev
 
 
+.. toctree::
+   :maxdepth: 2
+   :caption: Indices and Tables
 
+   chapters/all_exec
+   chapters/all_driver
 
 
-Indices and tables
-==================
-
 * :ref:`genindex`
 * :ref:`modindex`
 * :ref:`search`