[OP#162] Use the correct z index for the sidebar

[Jeremy-Walton]

Why?

The sidebar was not using a z index which caused the navbar (if used in combination) was covering up the sidebar border.

What Changed

• [X] Use the drawer z index on sidebar

Sanity Check

• ~~[ ] Have you updated any usage of changed tokens?~~
• ~~[ ] Have you updated the docs with any component changes?~~
• ~~[ ] Have you updated the dependency graph with any component changes?~~
• [X] Have you run linters?
• [X] Have you run prettier?
• [X] Have you tried building the css?
• [X] Have you tried building storybook?
• ~~[ ] Do you need to update the package version?~~

Screenshots

Before

After