chore: sync common files from resources repository

Author: metworkbot

README.md

@@ -12,6 +12,35 @@
 
 [//]: # (TABLE_OF_CONTENTS_PLACEHOLDER)
 
+## What is it ?
+
+This is a [jinja2](http://jinja.pocoo.org/) extension to execute system/shell
+commands from a template.
+
+**WARNING: be sure to valid any string submitted to this filter as you can
+open security holes with it**
+
+## Syntax
+
+The syntax is `'full_command_with_args'|shell([die_on_error_boolean_flag], [encoding])`.
+
+## Example
+
+```python
+
+from jinja2 import Template, Environment
+
+# We load the extension in a jinja2 Environment
+env = Environment(extensions=["jinja2_shell_extension.ShellExtension"])
+
+# For the example, we use a template from a simple string
+template = env.from_string("{{ 'date --rfc-2822'|shell() }}")
+result = template.render()
+
+# example: result == "Fri, 31 Jan 2020 13:35:56 +0100"
+# [...]
+
+```