Fix support button and ToC sidebar from appearing on top of zoomed-in images

[josh-wong]

Description

This PR fixes an issue where the sidebar that contains the support button and table of contents (ToC) was appearing on top of zoomed-in images. When clicking on an image, the sidebar that contains the support menu and ToC would appear on top of the zoomed-in image. The addition of the image styles in this PR ensures that the image overlays that sidebar.

Related issues and/or PRs

• Support button and dropdown added in Add support dropdown menu to right-hand sidebar of pages #1027.

Changes made

• Added styles for .medium-zoom-overlay and .medium-zoom-image to make zoomed-in images appear on top of the sidebar that contains the support button and ToC.
• Adjusted the style for the announcement bar to ensure that it stays visible when an image is zoomed in on.

Checklist

The following is a best-effort checklist. If any items in this checklist are not applicable to this PR or are dependent on other, unmerged PRs, please still mark the checkboxes after you have read and understood each item.

• I have updated the side navigation as necessary. N/A
• I have commented my code, particularly in hard-to-understand areas.
• I have updated the documentation to reflect the changes. N/A
• Any remaining open issues linked to this PR are documented and up-to-date (Jira, GitHub, etc.). N/A
• My changes generate no new warnings.
• Any dependent changes in other PRs have been merged and published. N/A

Additional notes (optional)

N/A