Codeblock Copy button styling broken in "classic" template

[Noah-Silvera]

🐛 Bug Report

The copy button styling for the codeblock in the "classic" template is broken. The "copy" text is dark against a dark background

Have you read the Contributing Guidelines on issues?

Yes

To Reproduce

1.Initialize a new docusaurus project using the create script and "classic" template
* https://v2.docusaurus.io/docs/installation#scaffold-project-website
2. Add a code block
3. Hover over the code block

Expected behavior

The copy button is activated, with the "copy" text clearly visible

Actual Behavior

The copy button text is dark against a dark background, so you cannot see the purpose of the button.

Your Environment

Docusaurus 2.0.0-alpha.50
Chrome Version 80.0.3987.149 (Official Build) (64-bit)

Reproducible Demo

https://github.com/Noah-Silvera/docusaurus-code-block-bug

[dalexhd]

I also had the same issue. Currently we will need to wait until next release. #2502 (comment)_

[lex111]

Sorry about this, as a workaround (temporary) solution, you can define your own Prism theme for dark mode as done on v2.