* Add channel design document

* Update channel send/recv state diagram

* Create go_op design doc

* Update index_en.rst

New file

* Update index_en.rst

Fix refer to suggestions

* Update index_en.rst

Update en version

* Update index_en.rst

Update refer to commits and thank you for the suggestion.

* Update index_en.rst

* Update index_en.rst

Update  refer to commits

* Add some contents

* Adjust the content of the English version

* Fix some error, replace word generate with build

* Replace document with documentation

* Adjust contents

* Make links more visible

change the path of image code

* Create select_op design document

* Fix pre-commit issues

* Update select op as per varun's comments

repair hyperlink format

fix space and toctree format

Done

fix https://github.com/PaddlePaddle/Paddle/issues/8921

fix #8956