Update coding_guidelines.rst: SCSS/CSS tabs

[ezoer]

Added implied SCSS variables to SCSS section Changed code formatting to comply with Odoo standards to ident with 4 spaces

[robodoo]

Pull request status dashboard.

[jcs-odoo]

Thanks for your PR @ezoer

Note: it should target 14.0 and not 16.0

Hi @AntoineVDV I think this is for you :)