PDF text hightlighting color

### Is there an existing issue outlining your problem?

- [X] I have searched the existing issues and they do not solve my problem.

### Describe your problem.

Opening a pdf file using the Mocha theme, everything is fine. But when I get to highlight text, the "hidden" text, made to be selected, when selected, becomes black. Thus macking this very bizzare look.

Usually, the text color should remain transparent. I have css knowledge, but have no clue how to get the class/ids of electron apps! Happy to help if needed.

### Attach screenshots.

Issue.

( Opening it in another window, removes theming ) This is what it should look like.

### What Logseq version do you see the issue on?

0.10.9

### What theme version do you see the issue on?

0.6.4

### Any additional comments?

_No response_

Reproduce PDF text highlighting in Logseq with the Mocha theme, using the attached screenshots and the reported Logseq and theme versions as reference. Inspect the theme's SCSS and the PDF text-selection styling to identify why selected hidden text becomes black; done means the text remains transparent while the highlight appearance matches the expected screenshot.

Written by the indexing model from the issue text.