Function getCssVariable

getCssVariable(cssVariable: string, fallbackValue: string): string
Returns the value of a CSS variable. If it is no defined, returns fallbackValue;
```
// Returns the value of --fg, or 'white' otherwise
getCssVariable(`--fg`, `white`);
```
-- prefix can be omitted:
```
getCssVariable(`fg`, `white`);
```
Parameters
- cssVariable: string
- fallbackValue: string
Returns string
- Defined in css-variables.ts:221