Function getCLS

getCLS(): Promise<number>
Gets the Cumulative Layout Shift (CLS) score of a web page using the Performance API. The CLS score is a measure of how much the page layout shifts during loading.

Usage:
```
getCLS().then(
 res => {
   console.log(`CLS: ${res}`);
 }
);
```
Output:
```
CLS: 123
```
Returns Promise<number>
A promise that resolves with the CLS score, or 0 if the 'layout-shift' entry type is not supported.
- Defined in index.ts:1858