RK-J

Just like rk-sidebar creates a box in the right hand side, we need to have rk-box that just creates a box around the content with a very light grey background.

For example, we need to ensure we have this box for the following
1. https://edutestdev-240612.appspot.com/document/pandas-development/meet?documentURL=10066%2Fpk20oct21%2Fdocs%2Fdevelopment%2Fcontributing_environment-Creating-an-environment-without-Docker-18.html - Box for Warning

2. https://edutestdev-240612.appspot.com/document/pandas-development/meet?documentURL=10066%2Fpk20oct21%2Fdocs%2Fdevelopment%2Fcontributing_environment-Creating-an-environment-without-Docker-18.html - Box for Code

3. https://edutestdev-240612.appspot.com/document/pandas-development/meet?documentURL=10066%2Fpk20oct21%2Fdocs%2Fdevelopment%2Fcontributing_documentation-About-the-pandas-documentation-22.html - Box for Notes