Function isXZ

isXZ(buffer: Buffer): boolean
Check if a buffer contains XZ compressed data by examining magic bytes.
Parameters
- buffer: Buffer
  Buffer to check (needs at least 6 bytes)
Returns boolean
true if the buffer starts with XZ magic bytes
Example
```
const compressed = await xzAsync(Buffer.from('Hello'));
console.log(isXZ(compressed)); // true
console.log(isXZ(Buffer.from('Hello'))); // false
```
- Defined in lzma.ts:761