[SPARK-3952] [Streaming] [PySpark] add Python examples in Streaming Programming Guide

Having Python examples in Streaming Programming Guide.

Also add RecoverableNetworkWordCount example.

Author: Davies Liu <[email protected]>
Author: Davies Liu <[email protected]>

Closes #2808 from davies/pyguide and squashes the following commits:

8d4bec4 [Davies Liu] update readme
26a7e37 [Davies Liu] fix format
3821c4d [Davies Liu] address comments, add missing file
7e4bb8a [Davies Liu] add Python examples in Streaming Programming Guide

Author: davies

docs/README.md

@@ -25,8 +25,7 @@ installing via the Ruby Gem dependency manager. Since the exact HTML output
 varies between versions of Jekyll and its dependencies, we list specific versions here
 in some cases:
 
-    $ sudo gem install jekyll -v 1.4.3
-    $ sudo gem uninstall kramdown -v 1.4.1
+    $ sudo gem install jekyll
     $ sudo gem install jekyll-redirect-from
 
 Execute `jekyll` from the `docs/` directory. Compiling the site with Jekyll will create a directory