VSCode themes are directly not compatible with monaco-editor themes. The problem here is that vscode uses tmGrammar tokens for colorization support while monaco uses its own code editor to generate language tokens. (See more about it here).
Yu can use monaco-textmate to make your monac-editor tmGrammar compatible.
Once the tokens are tmGrammar compatible, you need to convert vscode generated theme data to monaco-editor compatible api. This package does exactly that.
import { convertTheme, convertThemeFromDir } from 'monaco-vscode-textmate-theme-converter';
/*
* In vscode use command: `Developer: Generate Color Theme From Current Settings`
* Copy the generated JSON and use it as input for the function below.
*/
const theme : IVSCodeTheme = {...}
convertTheme(theme);
/*
* Convert multiple vscode themes to monaco themes.
* This function takes as arguments an input directory with generated vscode json files and generated output files with the same names at output directory.
*/
convertThemeFromDir(inputDir: './my-vscode-themes-collection-dir/in', outDir: './my-vscode-themes-collection-dir/out');