RI-7362 Added support for dark theme for the "Command Preview" drawer

[valkirilov]

Description

Make the background of the code snippet block in the "Command Preview" drawer to support dark theme.

Old	New

How it was tested

1. Open a connection to a new or existing Database
2. Go to the Search page from the top navbar

• If you don't have any indexes yet, you'll see the "Create Index" wizard
• Otherwise, you should trigger the creation process by clicking "Get Started" from the alert below the top navbar
• Or simply, go to the following URL manually: http://localhost:8080/:databaseId/vector-search/create-index

3. On the first step of the creation process, click on the "Proceed to index" button in the bottom right corner of the page
4. On the second step of the flow, click on the "Command preview" button under the index attributes to see the command that will be executed

PS: You can toggle the appearance from Settings -> General -> Color Theme

[github-actions]

Code Coverage - Frontend unit tests

St.❔	Category	Percentage	Covered / Total
🟢	Statements	81.9%	19703/24058
🟡	Branches	67.23%	8541/12704
🟡	Functions	75.95%	5223/6877
🟢	Lines	82.33%	19288/23428

Test suite run success

5074 tests passing in 666 suites.

Report generated by 🧪jest coverage report action from 4ddc886

[KrumTy]

nice