Sticky Column Header overlaps Dialogs

[felix9607]

Describe the bug
When having a Sticky-Column-Header of the ui5-table component, it overlaps any dialogs that pop up. Same behavior can be seen on the documentation website. (See screenshot)

To reproduce
Steps to reproduce the behavior:

1. Go to 'Table Docmentation'
2. Scroll down to Sticky-Column-Header, activate it, position it in the middle of the viewport
3. Open The style dialog on the right hand side

Expected behavior
Not to overlap and be darker

Screenshots

Context

• UI5 Web Components version: 1.0.0-rc.6

Affected components (if known)
UI5-Table
UI5-Dialog