Lib: Update shell footer

[saad-mo]

Component name

Update shell footer

Detailed description

We already have markup for the footer in the shell, need to update it with the right sap logo.

TODO:

• [ ] update shell footer in components
• [ ] add/update new documenation for shell
• [ ] https://sap.github.io/fundamental/layouts/shell-layout.html

[pavansokkenagaraj]

Can we have an option to remove the shell footer, if we do not want to use